New in version: 2.12.4 This guide shows you how to secure your FastMCP server using AWS Cognito user pools. Since AWS Cognito doesn’t support Dynamic Client Registration, this integration uses the OAuth Proxy pattern to bridge AWS Cognito’s traditional OAuth with MCP’s authentication requirements. It also includes robust JWT token validation, ensuring enterprise-grade authentication.

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Configuration

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Prerequisites

Before you begin, you will need:
  1. An AWS Account with access to create AWS Cognito user pools
  2. Basic familiarity with AWS Cognito concepts (user pools, app clients)
  3. Your FastMCP server’s URL (can be localhost for development, e.g., http://localhost:8000)

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Step 1: Create an AWS Cognito User Pool and App Client

Set up AWS Cognito user pool with an app client to get the credentials needed for authentication:
1

Navigate to AWS Cognito

Go to the AWS Cognito Console and ensure you’re in your desired AWS region.Select “User pools” from the side navigation (click on the hamburger icon at the top left in case you don’t see any), and click “Create user pool” to create a new user pool.
2

Define Your Application

AWS Cognito now provides a streamlined setup experience:
  1. Application type: Select “Traditional web application” (this is the correct choice for FastMCP server-side authentication)
  2. Name your application: Enter a descriptive name (e.g., FastMCP Server)
The traditional web application type automatically configures:
  • Server-side authentication with client secrets
  • Authorization code grant flow
  • Appropriate security settings for confidential clients
Choose “Traditional web application” rather than SPA, Mobile app, or Machine-to-machine options. This ensures proper OAuth 2.0 configuration for FastMCP.
3

Configure Options

AWS will guide you through configuration options:
  • Sign-in identifiers: Choose how users will sign in (email, username, or phone)
  • Required attributes: Select any additional user information you need
  • Return URL: Add your callback URL (e.g., http://localhost:8000/auth/callback for development)
The simplified interface handles most OAuth security settings automatically based on your application type selection.
4

Review and Create

Review your configuration and click “Create user pool”.After creation, you’ll see your user pool details. Save these important values:
  • User pool ID (format: eu-central-1_XXXXXXXXX)
  • Client ID (found under → “Applications” → “App clients” in the side navigation → <Your application name, e.g., FastMCP Server> → “App client information”)
  • Client Secret (found under → “Applications” → “App clients” in the side navigation → <Your application name, e.g., FastMCP Server> → “App client information”)
The user pool ID and app client credentials are all you need for FastMCP configuration.
5

Configure OAuth Settings

Under “Login pages” in your app client’s settings, you can double check and adjust the OAuth configuration:
  • Allowed callback URLs: Add your server URL + /auth/callback (e.g., http://localhost:8000/auth/callback)
  • Allowed sign-out URLs: Optional, for logout functionality
  • OAuth 2.0 grant types: Ensure “Authorization code grant” is selected
  • OpenID Connect scopes: Select scopes your application needs (e.g., openid, email, profile)
For local development, you can use http://localhost URLs. For production, you must use HTTPS.
6

Pick Up AWS Cognito Domain

Navigate to “Branding” → “Domain” in the side navigation to find or configure Your AWS Cognito domain:Option 1: Use Auto-Generated Domain
  • If AWS has already created a domain automatically, note the domain prefix (the part before .auth.region.amazoncognito.com)
  • This prefix is what you’ll use in your FastMCP configuration
Option 2: Create a Custom Domain Prefix
  • If no domain exists or you want a better name, delete the existing domain and create a new one using the “Actions” menu
  • Under “Domain” → “Cognito domain” in the “Create Cognito domain” dialog, enter a meaningful prefix (e.g., my-app) that is available in the AWS region you are in
  • Just note the domain prefix you entered (e.g., my-fastmcp-app) - this is what you’ll use in your FastMCP configuration
The FastMCP AWS Cognito provider automatically constructs the full domain from your prefix and region, simplifying configuration.
7

Save Your Credentials

After setup, you’ll have:
  • User Pool ID: Format like eu-central-1_XXXXXXXXX
  • Client ID: Your application’s client identifier
  • Client Secret: Generated client secret (keep secure)
  • Domain Prefix: The prefix of Your AWS Cognito domain
  • AWS Region: Where Your AWS Cognito user pool is located
Store these credentials securely. Never commit them to version control. Use environment variables or AWS Secrets Manager in production.

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Step 2: FastMCP Configuration

Create your FastMCP server using the AWSCognitoProvider, which handles AWS Cognito’s JWT tokens and user claims automatically:
server.py
from fastmcp import FastMCP
from fastmcp.server.auth.providers.aws import AWSCognitoProvider
from fastmcp.server.dependencies import get_access_token

# The AWSCognitoProvider handles JWT validation and user claims
auth_provider = AWSCognitoProvider(
    user_pool_id="eu-central-1_XXXXXXXXX",   # Your AWS Cognito user pool ID
    aws_region="eu-central-1",               # AWS region (defaults to eu-central-1)
    client_id="your-app-client-id",          # Your app client ID
    client_secret="your-app-client-secret",  # Your app client Secret
    base_url="http://localhost:8000",        # Must match your callback URL
    # redirect_path="/auth/callback"         # Default value, customize if needed
)

mcp = FastMCP(name="AWS Cognito Secured App", auth=auth_provider)

# Add a protected tool to test authentication
@mcp.tool
async def get_access_token_claims() -> dict:
    """Get the authenticated user's access token claims."""
    token = get_access_token()
    return {
        "sub": token.claims.get("sub"),
        "username": token.claims.get("username"),
        "cognito:groups": token.claims.get("cognito:groups", []),
    }

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Testing

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Running the Server

Start your FastMCP server with HTTP transport to enable OAuth flows: 
fastmcp run server.py --transport http --port 8000
Your server is now running and protected by AWS Cognito OAuth authentication.

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Testing with a Client

Create a test client that authenticates with Your AWS Cognito-protected server:
test_client.py
from fastmcp import Client
import asyncio

async def main():
    # The client will automatically handle AWS Cognito OAuth
    async with Client("http://localhost:8000/mcp/", auth="oauth") as client:
        # First-time connection will open AWS Cognito login in your browser
        print("✓ Authenticated with AWS Cognito!")

        # Test the protected tool
        print("Calling protected tool: get_access_token_claims")
        result = await client.call_tool("get_access_token_claims")
        user_data = result.data
        print("Available access token claims:")
        print(f"- sub: {user_data.get('sub', 'N/A')}")
        print(f"- username: {user_data.get('username', 'N/A')}")
        print(f"- cognito:groups: {user_data.get('cognito:groups', [])}")

if __name__ == "__main__":
    asyncio.run(main())
When you run the client for the first time:
  1. Your browser will open to AWS Cognito’s hosted UI login page
  2. After you sign in (or sign up), you’ll be redirected back to your MCP server
  3. The client receives the JWT token and can make authenticated requests
The client caches tokens locally, so you won’t need to re-authenticate for subsequent runs unless the token expires or you explicitly clear the cache.

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Environment Variables

For production deployments, use environment variables instead of hardcoding credentials.

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Provider Selection

Setting this environment variable allows the AWS Cognito provider to be used automatically without explicitly instantiating it in code.

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FASTMCP_SERVER_AUTH
default:"Not set"
Set to fastmcp.server.auth.providers.aws.AWSCognitoProvider to use AWS Cognito authentication.

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AWS Cognito-Specific Configuration

These environment variables provide default values for the AWS Cognito provider, whether it’s instantiated manually or configured via FASTMCP_SERVER_AUTH.

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FASTMCP_SERVER_AUTH_AWS_COGNITO_USER_POOL_ID
required
Your AWS Cognito user pool ID (e.g., eu-central-1_XXXXXXXXX)
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FASTMCP_SERVER_AUTH_AWS_COGNITO_AWS_REGION
default:"eu-central-1"
AWS region where your AWS Cognito user pool is located
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FASTMCP_SERVER_AUTH_AWS_COGNITO_CLIENT_ID
required
Your AWS Cognito app client ID
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FASTMCP_SERVER_AUTH_AWS_COGNITO_CLIENT_SECRET
required
Your AWS Cognito app client secret
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FASTMCP_SERVER_AUTH_AWS_COGNITO_BASE_URL
default:"http://localhost:8000"
Public URL of your FastMCP server for OAuth callbacks
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FASTMCP_SERVER_AUTH_AWS_COGNITO_REDIRECT_PATH
default:"/auth/callback"
One of the redirect paths configured in your AWS Cognito app client
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FASTMCP_SERVER_AUTH_AWS_COGNITO_REQUIRED_SCOPES
default:"[\"openid\"]"
Comma-, space-, or JSON-separated list of required OAuth scopes (e.g., openid email or ["openid","email","profile"])
Example .env file: 
# Use the AWS Cognito provider
FASTMCP_SERVER_AUTH=fastmcp.server.auth.providers.aws.AWSCognitoProvider

# AWS Cognito credentials
FASTMCP_SERVER_AUTH_AWS_COGNITO_USER_POOL_ID=eu-central-1_XXXXXXXXX
FASTMCP_SERVER_AUTH_AWS_COGNITO_AWS_REGION=eu-central-1
FASTMCP_SERVER_AUTH_AWS_COGNITO_CLIENT_ID=your-app-client-id
FASTMCP_SERVER_AUTH_AWS_COGNITO_CLIENT_SECRET=your-app-client-secret
FASTMCP_SERVER_AUTH_AWS_COGNITO_BASE_URL=https://your-server.com
FASTMCP_SERVER_AUTH_AWS_COGNITO_REQUIRED_SCOPES=openid,email,profile
With environment variables set, your server code simplifies to:
server.py
from fastmcp import FastMCP
from fastmcp.server.dependencies import get_access_token

# Authentication is automatically configured from environment
mcp = FastMCP(name="AWS Cognito Secured App")

@mcp.tool
async def get_access_token_claims() -> dict:
    """Get the authenticated user's access token claims."""
    token = get_access_token()
    return {
        "sub": token.claims.get("sub"),
        "username": token.claims.get("username"),
        "cognito:groups": token.claims.get("cognito:groups", []),
    }

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Features

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JWT Token Validation

The AWS Cognito provider includes robust JWT token validation:
  • Signature Verification: Validates tokens against AWS Cognito’s public keys (JWKS)
  • Expiration Checking: Automatically rejects expired tokens
  • Issuer Validation: Ensures tokens come from your specific AWS Cognito user pool
  • Scope Enforcement: Verifies required OAuth scopes are present

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User Claims and Groups

Access rich user information from AWS Cognito JWT tokens: 
from fastmcp.server.dependencies import get_access_token

@mcp.tool
async def admin_only_tool() -> str:
    """A tool only available to admin users."""
    token = get_access_token()
    user_groups = token.claims.get("cognito:groups", [])

    if "admin" not in user_groups:
        raise ValueError("This tool requires admin access")

    return "Admin access granted!"

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Enterprise Integration

Perfect for enterprise environments with:
  • Single Sign-On (SSO): Integrate with corporate identity providers
  • Multi-Factor Authentication (MFA): Leverage AWS Cognito’s built-in MFA
  • User Groups: Role-based access control through AWS Cognito groups
  • Custom Attributes: Access custom user attributes defined in your AWS Cognito user pool
  • Compliance: Meet enterprise security and compliance requirements