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Amazon Bedrock Agents

Create Amazon Bedrock Agents using event handlers with two different action groups approaches:

  • OpenAPI schema
  • Function details
flowchart LR
    Bedrock[LLM] <-- uses --> Agent
    You[User input] --> Agent
    Agent -- consults --> OpenAPI
    Agent -- consults --> Functions
    Agent[Amazon Bedrock Agents] -- invokes --> Lambda

    subgraph OpenAPI
        Schema
    end

    subgraph Functions
        ToolDescriptions[Tool Descriptions]
    end

    subgraph Lambda[Lambda Function]
        direction TB
        Parsing[Parameter Parsing] --> Validation
        Validation[Parameter Validation] --> Routing
        Routing --> Code[Your code]
        Code --> ResponseValidation[Response Validation]
        ResponseValidation --> ResponseBuilding[Response Building]
    end

    subgraph ActionGroup[Action Group]
        OpenAPI -. generated from .-> Lambda
        Functions -. defined in .-> Lambda
    end

    style Code fill:#ffa500,color:black,font-weight:bold,stroke-width:3px
    style You stroke:#0F0,stroke-width:2px

Key features

  • Minimal boilerplate to build Amazon Bedrock Agents
  • Support for both OpenAPI-based and Function-based actions
  • Automatic generation of OpenAPI schemas from your business logic code
  • Built-in data validation for requests and responses
  • Similar experience to authoring REST and HTTP APIs

Terminology

Data validation automatically validates the user input and the response of your AWS Lambda function against a set of constraints defined by you.

Event handler is a Powertools for AWS feature that processes an event, runs data parsing and validation, routes the request to a specific function, and returns a response to the caller in the proper format.

OpenAPI schema is an industry standard JSON-serialized string that represents the structure and parameters of your API.

Function details consist of a list of parameters, defined by their name, data type, and whether they are required. The agent uses these configurations to determine what information it needs to elicit from the user.

Action group is a collection of two resources where you define the actions that the agent should carry out when invoking your Lambda function.

Large Language Models (LLM) are very large deep learning models that are pre-trained on vast amounts of data, capable of extracting meanings from a sequence of text and understanding the relationship between words and phrases on it.

Amazon Bedrock Agent is an Amazon Bedrock feature to build and deploy conversational agents that can interact with your customers using Large Language Models (LLM) and AWS Lambda functions.

All examples shared in this documentation are available within the project repository

Choose your Action Group

An action group defines actions that the agent can help the user perform. You can define action groups as OpenAPI-based or Function-based.

Aspect OpenAPI-based Actions Function-based Actions
Definition Style @app.get("/path", description="")
@app.post("/path", description="")		 @app.tool(name="")
Parameter Handling Path, query, and body parameters Function parameters
Use Case REST-like APIs, complex request/response structures Direct function calls, simpler input
Response object Via BedrockResponse Via BedrockFunctionResponse
Best For - Complex APIs with multiple endpoints
- When OpenAPI spec is required
- Integration with existing REST APIs		 - Simple function-based actions
- Direct LLM-to-function mapping

Getting started

Install

This is unnecessary if you're installing Powertools for AWS Lambda (Python) via Lambda Layer/SAR.

If you define the action group setting up an OpenAPI schema, you need to add pydantic as a dependency in your preferred tool e.g., requirements.txt, pyproject.toml. At this time, we only support Pydantic V2.

Your first Agent

To create an agent, use the BedrockAgentResolver or the BedrockAgentFunctionResolver to annotate your actions. This is similar to the way all the other Event Handler resolvers work.

The resolvers used by Amazon Bedrock Agents are compatible with all Powertools for AWS Lambda features. For reference, we use Logger and Tracer in this example.

OpenAPI-based actions

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from time import time

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentResolver()


@app.get("/current_time", description="Gets the current time in seconds")  # (1)!
@tracer.capture_method
def current_time() -> int:
    return int(time())


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)  # (2)!
  1. description is a required field that should contain a human readable description of your action.
  2. We take care of parsing, validating, routing and responding to the request.

Powertools for AWS Lambda generates this automatically from the Lambda handler.

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{
  "openapi": "3.0.3",
  "info": {
    "title": "Powertools API",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/current_time": {
      "get": {
        "summary": "GET /current_time",
        "description": "Gets the current time in seconds",
        "operationId": "current_time_current_time_get",
        "responses": {
          "200": {
            "description": "Successful Response",
            "content": {
              "application/json": {
                "schema": {
                  "type": "integer",
                  "title": "Return"
                }
              }
            }
          },
          "422": {
            "description": "Validation Error",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/HTTPValidationError"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "HTTPValidationError": {
        "properties": {
          "detail": {
            "items": {
              "$ref": "#/components/schemas/ValidationError"
            },
            "type": "array",
            "title": "Detail"
          }
        },
        "type": "object",
        "title": "HTTPValidationError"
      },
      "ValidationError": {
        "properties": {
          "loc": {
            "items": {
              "anyOf": [
                {
                  "type": "string"
                },
                {
                  "type": "integer"
                }
              ]
            },
            "type": "array",
            "title": "Location"
          },
          "msg": {
            "type": "string",
            "title": "Message"
          },
          "type": {
            "type": "string",
            "title": "Error Type"
          }
        },
        "type": "object",
        "required": [
          "loc",
          "msg",
          "type"
        ],
        "title": "ValidationError"
      }
    }
  }
}

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{
  "sessionId": "123456789012345",
  "sessionAttributes": {},
  "inputText": "What is the current time?",
  "promptSessionAttributes": {},
  "apiPath": "/current_time",
  "agent": {
    "name": "TimeAgent",
    "version": "DRAFT",
    "id": "XLHH72XNF2",
    "alias": "TSTALIASID"
  },
  "httpMethod": "GET",
  "messageVersion": "1.0",
  "actionGroup": "CurrentTime"
}

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{
  "messageVersion": "1.0",
  "response": {
    "actionGroup": "CurrentTime",
    "apiPath": "/current_time",
    "httpMethod": "GET",
    "httpStatusCode": 200,
    "responseBody": {
      "application/json": {
        "body": "1704708165"
      }
    }
  }
}

Function-based actions

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from time import time

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentFunctionResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentFunctionResolver()


@app.tool(name="currentTime", description="Gets the current time in seconds")  # (1)!
@tracer.capture_method
def current_time() -> int:
    return int(time())


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)  # (2)!
  1. name and description are optional here.
  2. We take care of parsing, validating, routing and responding to the request.
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{
  "messageVersion": "1.0",
  "agent": {
    "name": "TimeAgent",
    "id": "XLHH72XNF2",
    "alias": "TSTALIASID",
    "version": "DRAFT"
  },
  "inputText": "What is the current time?",
  "sessionId": "123456789012345",
  "actionGroup": "CurrentTime",
  "function": "CurrentTime",
  "parameters": [],
  "sessionAttributes": {},
  "promptSessionAttributes": {}
}

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{
    "messageVersion": "1.0",
    "response": {
        "actionGroup": "CurrentTime",
        "function": "CurrentTime",
        "functionResponse": {
            "responseBody": {
                "application/json": {
                    "body": "1704708165"
                }
            }
        }
    }
}

Accessing custom request fields

The event sent by Amazon Bedrock Agents into your Lambda function contains a number of extra event fields, exposed in the app.current_event field.

Why is this useful?

You can for instance identify new conversations (session_id) or store and analyze entire conversations (input_text).

In this example, we append correlation data to all generated logs. This can be used to aggregate logs by session_id and observe the entire conversation between a user and the Agent.

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from time import time

from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

logger = Logger()
app = BedrockAgentResolver()


@app.get("/current_time", description="Gets the current time in seconds")
def current_time() -> int:
    logger.append_keys(
        session_id=app.current_event.session_id,
        action_group=app.current_event.action_group,
        input_text=app.current_event.input_text,
    )

    logger.info("Serving current_time")
    return int(time())


@logger.inject_lambda_context
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)

The input event fields available depend on your Agent's configuration (OpenAPI-based or Function-based):

Name Type Description OpenAPI Function
message_version str The version of the message format. Amazon Bedrock only supports version 1.0. ✅ ✅
agent BedrockAgentInfo Contains information about the name, ID, alias, and version of the agent. ✅ ✅
input_text str The user input for the conversation turn. ✅ ✅
session_id str The unique identifier of the agent session. ✅ ✅
action_group str The name of the action group. ✅ ✅
api_path str The path to the API operation, as defined in the OpenAPI schema. ✅ ❌
http_method str The method of the API operation, as defined in the OpenAPI schema. ✅ ❌
function str The name of the function being called. ❌ ✅
parameters List[Parameter] Contains parameters with name, type, and value properties. ✅ ✅
request_body BedrockAgentRequestBody Contains the request body and its properties. ✅ ❌
session_attributes Dict[str, str] Contains session attributes and their values. ✅ ✅
prompt_session_attributes Dict[str, str] Contains prompt attributes and their values. ✅ ✅

OpenAPI-based actions

Generating OpenAPI schemas

Use the get_openapi_json_schema function provided by the resolver to produce a JSON-serialized string that represents your OpenAPI schema. You can print this string or save it to a file. You'll use the file later when creating the Agent.

You'll need to regenerate the OpenAPI schema and update your Agent everytime your API changes.

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from time import time

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentResolver()


@app.get("/current_time", description="Gets the current time in seconds")
@tracer.capture_method
def current_time() -> int:
    return int(time())


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)


if __name__ == "__main__":  # (1)!
    print(app.get_openapi_json_schema())  # (2)!
  1. This ensures that it's only executed when running the file directly, and not when running on the Lambda runtime.
  2. You can use additional options to customize the OpenAPI schema.
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{
  "openapi": "3.0.3",
  "info": {
    "title": "Powertools API",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/current_time": {
      "get": {
        "summary": "GET /current_time",
        "description": "Gets the current time in seconds",
        "operationId": "current_time_current_time_get",
        "responses": {
          "200": {
            "description": "Successful Response",
            "content": {
              "application/json": {
                "schema": {
                  "type": "integer",
                  "title": "Return"
                }
              }
            }
          },
          "422": {
            "description": "Validation Error",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/HTTPValidationError"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "HTTPValidationError": {
        "properties": {
          "detail": {
            "items": {
              "$ref": "#/components/schemas/ValidationError"
            },
            "type": "array",
            "title": "Detail"
          }
        },
        "type": "object",
        "title": "HTTPValidationError"
      },
      "ValidationError": {
        "properties": {
          "loc": {
            "items": {
              "anyOf": [
                {
                  "type": "string"
                },
                {
                  "type": "integer"
                }
              ]
            },
            "type": "array",
            "title": "Location"
          },
          "msg": {
            "type": "string",
            "title": "Message"
          },
          "type": {
            "type": "string",
            "title": "Error Type"
          }
        },
        "type": "object",
        "required": [
          "loc",
          "msg",
          "type"
        ],
        "title": "ValidationError"
      }
    }
  }
}

To get the OpenAPI schema, run the Python script from your terminal. The script will generate the schema directly to standard output, which you can redirect to a file.

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python3 app.py > schema.json

Crafting effective OpenAPI schemas

Working with Amazon Bedrock Agents will introduce non-deterministic behaviour to your system.

Why is that?

Amazon Bedrock uses LLMs to understand and respond to user input. These models are trained on vast amounts of data and are capable of extracting meanings from a sequence of text and understanding the relationship between words and phrases on it. However, this means that the same input can result in different outputs, depending on the characteristics of the LLM being used.

The OpenAPI schema provides context and semantics to the Agent that will support the decision process for invoking our Lambda function. Sparse or ambiguous schemas can result in unexpected outcomes.

We recommend enriching your OpenAPI schema with as many details as possible to help the Agent understand your functions, and make correct invocations. To achieve that, keep the following suggestions in mind:

  • Always describe your function behaviour using the description field in your annotations
  • When refactoring, update your description field to match the function outcomes
  • Use distinct description for each function to have clear separation of semantics

Validating input and output

You can define the expected format for incoming data and responses by using type annotations. Define constraints using standard Python types, dataclasses or Pydantic models. Pydantic is a popular library for data validation using Python type annotations.

The examples below uses Pydantic's EmailStr to validate the email address passed to the schedule_meeting function. The function then returns a boolean indicating if the meeting was successfully scheduled.

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from pydantic import EmailStr
from typing_extensions import Annotated

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.event_handler.openapi.params import Body, Query
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentResolver()  # (1)!


@app.get("/schedule_meeting", description="Schedules a meeting with the team")
@tracer.capture_method
def schedule_meeting(
    email: Annotated[EmailStr, Query(description="The email address of the customer")],  # (2)!
) -> Annotated[bool, Body(description="Whether the meeting was scheduled successfully")]:  # (3)!
    logger.info("Scheduling a meeting", email=email)
    return True


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)
  1. No need to add the enable_validation parameter, as it's enabled by default.
  2. Describe each input using human-readable descriptions
  3. Add the typing annotations to your parameters and return types, and let the event handler take care of the rest
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{
  "openapi": "3.0.3",
  "info": {
    "title": "Powertools API",
    "version": "1.0.0"
  },
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/schedule_meeting": {
      "get": {
        "summary": "GET /schedule_meeting",
        "description": "Schedules a meeting with the team",
        "operationId": "schedule_meeting_schedule_meeting_get",
        "parameters": [
          {
            "description": "The email address of the customer",
            "required": true,
            "schema": {
              "type": "string",
              "format": "email",
              "title": "Email",
              "description": "The email address of the customer"
            },
            "name": "email",
            "in": "query"
          }
        ],
        "responses": {
          "200": {
            "description": "Successful Response",
            "content": {
              "application/json": {
                "schema": {
                  "type": "boolean",
                  "title": "Return",
                  "description": "Whether the meeting was scheduled successfully"
                }
              }
            }
          },
          "422": {
            "description": "Validation Error",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/HTTPValidationError"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "HTTPValidationError": {
        "properties": {
          "detail": {
            "items": {
              "$ref": "#/components/schemas/ValidationError"
            },
            "type": "array",
            "title": "Detail"
          }
        },
        "type": "object",
        "title": "HTTPValidationError"
      },
      "ValidationError": {
        "properties": {
          "loc": {
            "items": {
              "anyOf": [
                {
                  "type": "string"
                },
                {
                  "type": "integer"
                }
              ]
            },
            "type": "array",
            "title": "Location"
          },
          "msg": {
            "type": "string",
            "title": "Message"
          },
          "type": {
            "type": "string",
            "title": "Error Type"
          }
        },
        "type": "object",
        "required": [
          "loc",
          "msg",
          "type"
        ],
        "title": "ValidationError"
      }
    }
  }
}

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{
  "sessionId": "123456789012345",
  "sessionAttributes": {},
  "inputText": "Schedule a meeting with the team. My email is [email protected]",
  "promptSessionAttributes": {},
  "apiPath": "/schedule_meeting",
  "parameters": [
    {
      "name": "email",
      "type": "string",
      "value": "[email protected]"
    }
  ],
  "agent": {
    "name": "TimeAgent",
    "version": "DRAFT",
    "id": "XLHH72XNF2",
    "alias": "TSTALIASID"
  },
  "httpMethod": "GET",
  "messageVersion": "1.0",
  "actionGroup": "SupportAssistant"
}

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{
  "messageVersion": "1.0",
  "response": {
    "actionGroup": "SupportAssistant",
    "apiPath": "/schedule_meeting",
    "httpMethod": "GET",
    "httpStatusCode": 200,
    "responseBody": {
      "application/json": {
        "body": "true"
      }
    }
  }
}

When validation fails

If the request validation fails, your event handler will not be called, and an error message is returned to Bedrock. Similarly, if the response fails validation, your handler will abort the response.

What does this mean for my Agent?

The event handler will always return a response according to the schema (OpenAPI) or type hints (Function-based). A validation failure in OpenAPI-based actions results in a 422 response. For both approaches, how Amazon Bedrock interprets that failure is non-deterministic, since it depends on the characteristics of the LLM being used.

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{
  "sessionId": "123456789012345",
  "sessionAttributes": {},
  "inputText": "Schedule a meeting with the team. My email is foo@example@org",
  "promptSessionAttributes": {},
  "apiPath": "/schedule_meeting",
  "parameters": [
    {
      "name": "email",
      "type": "string",
      "value": "foo@example@org"
    }
  ],
  "agent": {
    "name": "TimeAgent",
    "version": "DRAFT",
    "id": "XLHH72XNF2",
    "alias": "TSTALIASID"
  },
  "httpMethod": "GET",
  "messageVersion": "1.0",
  "actionGroup": "SupportAssistant"
}

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{
  "messageVersion": "1.0",
  "response": {
    "actionGroup": "SupportAssistant",
    "apiPath": "/schedule_meeting",
    "httpMethod": "GET",
    "httpStatusCode": 200,
    "responseBody": {
      "application/json": {
        "body": "{\"statusCode\":422,\"detail\":[{\"loc\":[\"query\",\"email\"],\"type\":\"value_error.email\"}]}"
      }
    }
  }
}

sequenceDiagram
    Agent->>Lambda: input payload
    activate Lambda
    Lambda->>Parsing: parses input parameters
    Parsing->>Validation: validates input
    Validation-->Validation: failure
    box BedrockAgentResolver
    participant Lambda
    participant Parsing
    participant Validation
    participant Routing
    participant Your Code
    end
    Note right of Validation: Your code is never called
    Validation->>Agent: 422 response
    deactivate Lambda

Video walkthrough

To create an Agent for Amazon Bedrock, refer to the official documentation provided by AWS.

The following video demonstrates the end-to-end process:

During the creation process, you should use the schema previously generated when prompted for an OpenAPI specification.

Advanced

Additional metadata

To enrich the view that Amazon Bedrock Agents has of your Lambda functions, use a combination of Pydantic Models and OpenAPI type annotations to add constraints to your APIs parameters.

When is this useful?

Adding constraints to your function parameters can help you to enforce data validation and improve the understanding of your APIs by Amazon Bedrock.

Customizing OpenAPI parameters

Whenever you use OpenAPI parameters to validate query strings or path parameters, you can enhance validation and OpenAPI documentation by using any of these parameters:

Field name Type Description
alias str Alternative name for a field, used when serializing and deserializing data
validation_alias str Alternative name for a field during validation (but not serialization)
serialization_alias str Alternative name for a field during serialization (but not during validation)
description str Human-readable description
gt float Greater than. If set, value must be greater than this. Only applicable to numbers
ge float Greater than or equal. If set, value must be greater than or equal to this. Only applicable to numbers
lt float Less than. If set, value must be less than this. Only applicable to numbers
le float Less than or equal. If set, value must be less than or equal to this. Only applicable to numbers
min_length int Minimum length for strings
max_length int Maximum length for strings
pattern string A regular expression that the string must match.
strict bool If True, strict validation is applied to the field. See Strict Mode for details
multiple_of float Value must be a multiple of this. Only applicable to numbers
allow_inf_nan bool Allow inf, -inf, nan. Only applicable to numbers
max_digits int Maximum number of allow digits for strings
decimal_places int Maximum number of decimal places allowed for numbers
openapi_examples dict[str, Example] A list of examples to be displayed in the SwaggerUI interface. Avoid using the examples field for this purpose.
deprecated bool Marks the field as deprecated
include_in_schema bool If False the field will not be part of the exported OpenAPI schema
json_schema_extra JsonDict Any additional JSON schema data for the schema property

To implement these customizations, include extra constraints when defining your parameters:

Customizing API parameters
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import requests
from typing_extensions import Annotated

from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.event_handler.openapi.params import Body, Query
from aws_lambda_powertools.utilities.typing import LambdaContext

app = BedrockAgentResolver()

logger = Logger()


@app.post(
    "/todos",
    description="Creates a TODO",
)
def create_todo(
    title: Annotated[str, Query(max_length=200, strict=True, description="The TODO title")],  # (1)!
) -> Annotated[bool, Body(description="Was the TODO created correctly?")]:
    todo = requests.post("https://jsonplaceholder.typicode.com/todos", data={"title": title})
    try:
        todo.raise_for_status()
        return True
    except Exception:
        logger.exception("Error creating TODO")
        return False


def lambda_handler(event: dict, context: LambdaContext) -> dict:
    return app.resolve(event, context)
  1. Title should not be larger than 200 characters and strict mode is activated

Customizing API operations

Customize your API endpoints by adding metadata to endpoint definitions.

Here's a breakdown of various customizable fields:

Field Name Type Description
summary str A concise overview of the main functionality of the endpoint. This brief introduction is usually displayed in autogenerated API documentation and helps consumers quickly understand what the endpoint does.
description str A more detailed explanation of the endpoint, which can include information about the operation's behavior, including side effects, error states, and other operational guidelines.
responses Dict[int, Dict[str, OpenAPIResponse]] A dictionary that maps each HTTP status code to a Response Object as defined by the OpenAPI Specification. This allows you to describe expected responses, including default or error messages, and their corresponding schemas or models for different status codes.
response_description str Provides the default textual description of the response sent by the endpoint when the operation is successful. It is intended to give a human-readable understanding of the result.
tags List[str] Tags are a way to categorize and group endpoints within the API documentation. They can help organize the operations by resources or other heuristic.
operation_id str A unique identifier for the operation, which can be used for referencing this operation in documentation or code. This ID must be unique across all operations described in the API.
include_in_schema bool A boolean value that determines whether or not this operation should be included in the OpenAPI schema. Setting it to False can hide the endpoint from generated documentation and schema exports, which might be useful for private or experimental endpoints.
deprecated bool A boolean value that determines whether or not this operation should be marked as deprecated in the OpenAPI schema.

To implement these customizations, include extra parameters when defining your routes:

Customzing API operations
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import requests
from typing_extensions import Annotated

from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.event_handler.openapi.params import Body, Path
from aws_lambda_powertools.utilities.typing import LambdaContext

app = BedrockAgentResolver()


@app.get(
    "/todos/<todo_id>",
    summary="Retrieves a TODO item, returning it's title",
    description="Loads a TODO item identified by the `todo_id`",
    response_description="The TODO title",
    responses={
        200: {"description": "TODO item found"},
        404: {
            "description": "TODO not found",
        },
    },
    tags=["todos"],
)
def get_todo_title(
    todo_id: Annotated[int, Path(description="The ID of the TODO item from which to retrieve the title")],
) -> Annotated[str, Body(description="The TODO title")]:
    todo = requests.get(f"https://jsonplaceholder.typicode.com/todos/{todo_id}")
    todo.raise_for_status()

    return todo.json()["title"]


def lambda_handler(event: dict, context: LambdaContext) -> dict:
    return app.resolve(event, context)

Enabling user confirmation

You can enable user confirmation with Bedrock Agents to have your application ask for explicit user approval before invoking an action.

Enabling user confirmation
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from time import time

from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

logger = Logger()
app = BedrockAgentResolver()


@app.get(
    "/current_time",
    description="Gets the current time in seconds",
    openapi_extensions={"x-requireConfirmation": "ENABLED"},  # (1)!
)
def current_time() -> int:
    return int(time())


@logger.inject_lambda_context
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)


if __name__ == "__main__":
    print(app.get_openapi_json_schema())
  1. Add an openapi extension

OpenAPI-based Responses

Note

The default response only includes the essential fields to keep the payload size minimal, as AWS Lambda has a maximum response size of 25 KB.

You can use BedrockResponse class to add additional fields as needed, such as session attributes, prompt session attributes, and knowledge base configurations.

Customzing your Bedrock Response
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from http import HTTPStatus

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.event_handler.api_gateway import BedrockResponse
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentResolver()


@app.get("/return_with_session", description="Returns a hello world with session attributes")
@tracer.capture_method
def hello_world():
    return BedrockResponse(
        status_code=HTTPStatus.OK.value,
        body={"message": "Hello from Bedrock!"},
        session_attributes={"user_id": "123"},
        prompt_session_attributes={"context": "testing"},
        knowledge_bases_configuration=[
            {
                "knowledgeBaseId": "kb-123",
                "retrievalConfiguration": {
                    "vectorSearchConfiguration": {"numberOfResults": 3, "overrideSearchType": "HYBRID"},
                },
            },
        ],
    )


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)

Bedrock requests under the hood

Powertools handle the request from the Agent, parse, validate, and route it to the correct method in your code. The response is then validated and formatted back to the Agent.

sequenceDiagram
    actor User

    User->>Agent: What is the current time?
    Agent->>OpenAPI schema: consults
    OpenAPI schema-->>Agent: GET /current_time
    Agent-->>Agent: LLM interaction

    box Powertools
        participant Lambda
        participant Parsing
        participant Validation
        participant Routing
        participant Your Code
    end

    alt Function-based
        Agent->>Lambda: {function: "current_time", parameters: [], ...}
    end

    activate Lambda
    Lambda->>Parsing: parses parameters
    Parsing->>Validation: validates input
    Validation->>Routing: finds method to call
    Routing->>Your Code: executes
    activate Your Code
    Your Code->>Routing: 1709215709
    deactivate Your Code
    Routing->>Validation: returns output
    Validation->>Parsing: validates output
    Parsing->>Lambda: formats response

    alt Function-based
        Lambda->>Agent: {response: {functionResponse: {responseBody: {...}}}}
    end
    deactivate Lambda

    Agent-->>Agent: LLM interaction
    Agent->>User: "The current time is 14:08:29 GMT"

Testing your code

Test your routes by passing an Agent for Amazon Bedrock proxy event request:

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from dataclasses import dataclass

import assert_bedrock_agent_response_module
import pytest


@dataclass
class LambdaContext:
    function_name: str = "test"
    memory_limit_in_mb: int = 128
    invoked_function_arn: str = "arn:aws:lambda:eu-west-1:123456789012:function:test"
    aws_request_id: str = "da658bd3-2d6f-4e7b-8ec2-937234644fdc"


@pytest.fixture
def lambda_context() -> LambdaContext:
    return LambdaContext()


def test_lambda_handler(lambda_context: LambdaContext):
    minimal_event = {
        "apiPath": "/current_time",
        "httpMethod": "GET",
        "inputText": "What is the current time?",
    }
    # Example of Bedrock Agent API request event:
    # https://docs.aws.amazon.com/bedrock/latest/userguide/agents-lambda.html#agents-lambda-input
    ret = assert_bedrock_agent_response_module.lambda_handler(minimal_event, lambda_context)
    assert ret["response"]["httpStatuScode"] == 200
    assert ret["response"]["responseBody"]["application/json"]["body"] != ""

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import time

from typing_extensions import Annotated

from aws_lambda_powertools import Logger, Tracer
from aws_lambda_powertools.event_handler import BedrockAgentResolver
from aws_lambda_powertools.event_handler.openapi.params import Body
from aws_lambda_powertools.utilities.typing import LambdaContext

tracer = Tracer()
logger = Logger()
app = BedrockAgentResolver()


@app.get("/current_time", description="Gets the current time")
@tracer.capture_method
def current_time() -> Annotated[int, Body(description="Current time in milliseconds")]:
    return round(time.time() * 1000)


@logger.inject_lambda_context
@tracer.capture_lambda_handler
def lambda_handler(event: dict, context: LambdaContext) -> dict:
    return app.resolve(event, context)

Function-based Actions

The BedrockAgentFunctionResolver streamlines agent function development through three core capabilities:

  • Register Functions: Use the @app.tool() decorator to expose your functions to Bedrock Agents
Field Required Description
name No Custom name for your function. Uses the actual function name if omitted.
description No Explain what your function does to guide the agent's usage.
  • Process Parameters: Automatically maps input parameters from the agent to your function arguments
  • Format Responses: Transforms your function outputs into properly structured Bedrock Agent responses

Function-based Responses

Note

The default response only includes the essential fields to keep the payload size minimal, as AWS Lambda has a maximum response size of 25 KB.

You can use BedrockFunctionResponse class to customize your response with additional fields. This class allows you to:

  • Return a response body
  • Set session and prompt session attributes
  • Set knowledge bases configurations
  • Control the response state ("FAILURE" or "REPROMPT")
Customzing your Bedrock Function Response
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from aws_lambda_powertools.event_handler import BedrockAgentFunctionResolver, BedrockFunctionResponse
from aws_lambda_powertools.utilities.typing.lambda_context import LambdaContext

app = BedrockAgentFunctionResolver()


@app.tool(description="Function that demonstrates response customization")
def custom_response():
    return BedrockFunctionResponse(
        body="Hello World",
        session_attributes={"user_id": "123"},
        prompt_session_attributes={"last_action": "greeting"},
        response_state="REPROMPT",
        knowledge_bases=[{"name": "kb1", "enabled": True}],
    )


def lambda_handler(event: dict, context: LambdaContext):
    return app.resolve(event, context)