langchain

Example: LangChain

This example demonstrates how to use aws_iam_streamablehttp_client from mcp-proxy-for-aws to connect a LangChain AI agent to an MCP server using AWS IAM authentication.

Note: LangChain requires direct access to MCP sessions. The aws_iam_streamablehttp_client provides the authenticated transport streams, which are then used to create an MCP ClientSession.

Prerequisites

• Python 3.10+ and uv installed
• AWS credentials configured (via AWS CLI, environment variables, or IAM roles)
• Access to Anthropic Claude on Amazon Bedrock

Setup

Create a .env file or set the following environment variables:

# MCP server details
MCP_SERVER_URL=https://example.gateway.bedrock-agentcore.us-west-2.amazonaws.com/mcp
MCP_SERVER_AWS_SERVICE=bedrock-agentcore
MCP_SERVER_REGION=us-west-2

All three environment variables are required.

Usage

Run the example:

uv run main.py

The agent will connect to the MCP server and list its available tools.

How It Works

1. Loads configuration from environment variables or .env file
2. Creates an AWS IAM-authenticated MCP client using aws_iam_streamablehttp_client()
3. Extracts transport streams from the client context manager
4. Creates an MCP ClientSession with the authenticated transport streams
5. Loads MCP tools using LangChain's MCP tools adapter
6. Creates an agent with access to the MCP server tools
7. Runs the agent to demonstrate tool discovery and usage

Example MCP Server URL Formats

AgentCore Runtime URL:

https://bedrock-agentcore.[AWS_REGION].amazonaws.com/runtimes/[RUNTIME_ID]/invocations?qualifier=DEFAULT&accountId=[AWS_ACCOUNT_ID]

AgentCore Gateway URL:

https://[GATEWAY_ID].gateway.bedrock-agentcore.[AWS_REGION].amazonaws.com/mcp

Troubleshooting

Common Issues

No AWS credentials available

• Verify AWS credentials are configured (AWS CLI, environment variables, or IAM roles)
• Test with aws sts get-caller-identity

Missing environment variables

• Ensure all required variables are set: MCP_SERVER_URL, MCP_SERVER_REGION, and MCP_SERVER_AWS_SERVICE
• Check your .env file or environment variable configuration

Connection errors

• Verify your MCP server details are correct
• Ensure the MCP server is running and accessible
• Verify your AWS credentials have the necessary permissions to access the MCP server