Executing the Logic: Lambda Tools

When a Bedrock Agent decides to call a tool (e.g., get_user_email), it sends a request to an AWS Lambda function. The Lambda function executes the code (searching a DB, calling an external API) and returns the result to the agent.

1. The Lambda Event Structure

Bedrock sends a specific JSON "Event" to your Lambda. Your code must parse it to find the Action Group and Parameters.

import json

def lambda_handler(event, context):
    action_group = event['actionGroup']
    function = event['function']
    parameters = event['parameters']
    
    # Logic based on the function name
    if function == 'get_order_status':
        order_id = parameters[0]['value']
        # Call your database here...
        result = f"Order {order_id} is currently: SHIPPED"
        
    # Standard Bedrock Response Format
    response = {
        'actionGroup': action_group,
        'function': function,
        'functionResponse': {
            'responseBody': {
                'TEXT': {
                    'body': result
                }
            }
        }
    }
    
    return {'response': response}

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2. Security and Permissions

• The Agent must have permission to lambda:InvokeFunction.
• The Lambda must have a Resource-based Policy allowing the Bedrock service principal (bedrock.amazonaws.com) to call it.

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3. Visualizing the Execution Flow

graph LR
    Agent[Agent Brain] -->|Request Params| L[AWS Lambda]
    L -->|DB Query| DB[(Postgres)]
    DB -->|Data| L
    L -->|Format: TEXT| Agent
    Agent -->|Synthesize| User[Human Answer]

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💡 Guidance for Learners

Keep your Lambda functions Small. One Lambda can handle 5-10 different "Tools" in an Action Group using if/else logic. This makes management much easier than having 50 separate Lambda functions.

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Summary

• Lambda provides the "Muscle" for Bedrock Agent actions.
• You must follow a specific JSON Response Schema for Bedrock to understand the result.
• Permissions must be configured on both the Agent and the Lambda.
• Lambda allows your AI to interact with any AWS service or external API.