How do I use auth0-3lo-mcp-server?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@auth0-3lo-mcp-server whoami" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

auth0-3lo-mcp-server

by Neloh

Overview Schema Related Servers Score Discussions

Python

Remote

AgentCore Gateway 3LO: End-to-End Authorization Code Flow with Auth0

A complete working example of the Amazon Bedrock AgentCore Gateway 3-Legged OAuth (Authorization Code) flow using Auth0 as both the inbound JWT authorizer and the outbound credential provider, with a Lambda MCP server as the target.

What This Demonstrates

Inbound JWT authentication (Auth0 token → Gateway)
tools/list discovering tools from a remote MCP server
tools/call triggering a -32042 OAuth elicitation
User completing OAuth consent at Auth0
Callback handler receiving the session_id
CompleteResourceTokenAuth binding the token to the user
Subsequent tools/call succeeding end-to-end

Related MCP server: Remote MCP AuthKit

Architecture

MCP Client (curl) --> AgentCore Gateway --> Lambda MCP Server
       |                    |
       |                    +--> AgentCore Identity (token store)
       |                                |
       |                                +--> Auth0 (consent + code exchange)
       |
       +--> Callback Handler (Flask @ localhost:5000)
                    |
                    +--> Receives session_id after consent
                    +--> Calls CompleteResourceTokenAuth

Sequence Diagram

Prerequisites

AWS account with Amazon Bedrock AgentCore access
AWS CLI with bedrock-agentcore and bedrock-agentcore-control commands
Auth0 free developer account (sign up)
Python 3.12+
pip

Quick Start

# Clone this repo
git clone <repo-url>
cd agentcore-3lo-auth0-example

# Install dependencies
pip install -r requirements.txt

# Copy and fill in your credentials
cp .env.example .env
# Edit .env with your Auth0 and AWS values

# Start the Flask app
python app.py

Then follow the step-by-step guide below.

Step-by-Step Guide

Step 1: Auth0 Configuration

Create an API

Auth0 Dashboard > APIs > Create API
Name: agentcore-gateway-api
Identifier: https://agentcore-gateway-api
Signing Algorithm: RS256

Configure API Settings

Permissions tab: Add access:tools (description: "Access MCP tools")
Settings tab: Set "Allow Skipping User Consent" to OFF

API Permissions API Settings - Consent

Create an Application

Auth0 Dashboard > Applications > Create Application
Name: agentcore-3lo-repro, Type: Regular Web Application
Settings:
- Allowed Callback URLs: http://localhost:5000/callback, http://localhost:5000/token-callback
- Allowed Logout URLs: http://localhost:5000/

You will add the AgentCore callback URL to this list in Step 4.

App Settings

Auth0 Dashboard > Actions > Library > Build Custom
Name: add-scp-claim, Trigger: Login / Post Login

exports.onExecutePostLogin = async (event, api) => {
  const scopes = event.transaction.requested_scopes || [];
  if (!scopes.includes('openid')) {
    scopes.push('openid');
  }
  api.accessToken.setCustomClaim('scp', scopes);
};

Deploy, then add to the Login flow (Actions > Flows > Login)

Step 2: AWS IAM Role

Create an execution role for the Gateway with trust policy for bedrock-agentcore.amazonaws.com:

{
  "Version": "2012-10-17",
  "Statement": [
    {"Effect": "Allow", "Action": "bedrock-agentcore:*", "Resource": "*"},
    {"Effect": "Allow", "Action": "lambda:InvokeFunction", "Resource": "*"},
    {"Effect": "Allow", "Action": "secretsmanager:GetSecretValue",
     "Resource": "arn:aws:secretsmanager:<region>:<account>:secret:bedrock-agentcore-identity*"}
  ]
}

Step 3: Create AgentCore Gateway

Important: Use only allowedAudience. Do NOT use allowedClients with Auth0 — Auth0 places client_id in the azp claim, not client_id, causing insufficient_scope errors.

aws bedrock-agentcore-control create-gateway \
  --name "auth0-3lo-example" \
  --role-arn "arn:aws:iam::<account>:role/<role-name>" \
  --protocol-type MCP \
  --protocol-configuration '{"mcp":{"supportedVersions":["2025-11-25"]}}' \
  --authorizer-type CUSTOM_JWT \
  --authorizer-configuration '{
    "customJWTAuthorizer": {
      "discoveryUrl": "https://<tenant>.us.auth0.com/.well-known/openid-configuration",
      "allowedAudience": ["https://agentcore-gateway-api"]
    }
  }' \
  --region us-east-1

Wait for status: READY.

Step 4: Create OAuth2 Credential Provider

aws bedrock-agentcore-control create-oauth2-credential-provider \
  --name "auth0-3lo-example" \
  --credential-provider-vendor "CustomOauth2" \
  --oauth2-provider-config-input '{
    "customOauth2ProviderConfig": {
      "oauthDiscovery": {
        "authorizationServerMetadata": {
          "issuer": "https://<tenant>.us.auth0.com/",
          "authorizationEndpoint": "https://<tenant>.us.auth0.com/authorize",
          "tokenEndpoint": "https://<tenant>.us.auth0.com/oauth/token",
          "responseTypes": ["code"]
        }
      },
      "clientId": "<your-client-id>",
      "clientSecret": "<your-client-secret>",
      "clientAuthenticationMethod": "CLIENT_SECRET_POST"
    }
  }' \
  --region us-east-1

The response includes a callbackUrl. Add this URL to your Auth0 application's Allowed Callback URLs.

Step 5: Register Workload Identity Return URL

aws bedrock-agentcore-control update-workload-identity \
  --name "<gateway-id>" \
  --allowed-resource-oauth2-return-urls '["http://localhost:5000/agentcore-callback"]' \
  --region us-east-1

Step 6: Create Lambda MCP Server

Deploy the included Lambda function (see lambda/ directory):

cd lambda && zip -r ../lambda.zip . && cd ..

aws lambda create-function \
  --function-name auth0-3lo-mcp-server \
  --runtime python3.12 \
  --handler lambda_function.lambda_handler \
  --role arn:aws:iam::<account>:role/<lambda-role> \
  --zip-file fileb://lambda.zip \
  --region us-east-1

aws lambda create-function-url-config \
  --function-name auth0-3lo-mcp-server \
  --auth-type NONE \
  --region us-east-1

aws lambda add-permission \
  --function-name auth0-3lo-mcp-server \
  --statement-id FunctionURLAllowPublicAccess \
  --action lambda:InvokeFunctionUrl \
  --principal "*" \
  --function-url-auth-type NONE \
  --region us-east-1

Step 7: Create Gateway Target

aws bedrock-agentcore-control create-gateway-target \
  --gateway-identifier "<gateway-id>" \
  --name "auth0-3lo-lambda-mcp" \
  --target-configuration '{
    "mcp": {
      "mcpServer": {
        "endpoint": "<lambda-function-url>",
        "mcpToolSchema": {
          "inlinePayload": "{\"tools\":[{\"name\":\"whoami\",\"description\":\"Returns user info\",\"inputSchema\":{\"type\":\"object\",\"properties\":{},\"required\":[]}},{\"name\":\"echo\",\"description\":\"Echoes input\",\"inputSchema\":{\"type\":\"object\",\"properties\":{\"message\":{\"type\":\"string\"}},\"required\":[\"message\"]}}]}"
        }
      }
    }
  }' \
  --credential-provider-configurations '[{
    "credentialProviderType": "OAUTH",
    "credentialProvider": {
      "oauthCredentialProvider": {
        "providerArn": "arn:aws:bedrock-agentcore:us-east-1:<account>:token-vault/default/oauth2credentialprovider/auth0-3lo-example",
        "scopes": ["openid", "profile", "email"],
        "grantType": "AUTHORIZATION_CODE",
        "defaultReturnUrl": "http://localhost:5000/agentcore-callback",
        "customParameters": {
          "audience": "https://agentcore-gateway-api"
        }
      }
    }
  }]' \
  --region us-east-1

Step 8: Get an Access Token

Start Flask: python app.py
Open http://localhost:5000/token in your browser
Log in to Auth0
Copy the access token displayed

Step 9: Test the Flow

TOKEN="<your-access-token>"
GATEWAY="<gateway-id>"

# 1. List tools (confirms inbound auth)
curl -s -X POST "https://${GATEWAY}.gateway.bedrock-agentcore.us-east-1.amazonaws.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${TOKEN}" \
  -H "MCP-Protocol-Version: 2025-11-25" \
  -d '{"jsonrpc":"2.0","id":"1","method":"tools/list","params":{}}'

# 2. Call a tool (triggers -32042 elicitation)
curl -s -X POST "https://${GATEWAY}.gateway.bedrock-agentcore.us-east-1.amazonaws.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${TOKEN}" \
  -H "MCP-Protocol-Version: 2025-11-25" \
  -d '{"jsonrpc":"2.0","id":"1","method":"tools/call","params":{"name":"auth0-3lo-lambda-mcp___echo","arguments":{"message":"hello"}}}'

# 3. Open the URL from the -32042 response IMMEDIATELY (60s TTL)
#    Complete consent in browser
#    Browser lands on localhost:5000/agentcore-callback?session_id=...

# 4. Complete token binding
SESSION_ID="<session_id_from_callback>"
aws bedrock-agentcore complete-resource-token-auth \
  --user-identifier "{\"userToken\":\"${TOKEN}\"}" \
  --session-uri "${SESSION_ID}" \
  --region us-east-1

# 5. Retry the tool call (should succeed now)
curl -s -X POST "https://${GATEWAY}.gateway.bedrock-agentcore.us-east-1.amazonaws.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${TOKEN}" \
  -H "MCP-Protocol-Version: 2025-11-25" \
  -d '{"jsonrpc":"2.0","id":"1","method":"tools/call","params":{"name":"auth0-3lo-lambda-mcp___echo","arguments":{"message":"hello from 3LO end-to-end"}}}'

Expected final response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "content": [{"type": "text", "text": "Echo: hello from 3LO end-to-end"}]
  }
}

Callback Received

Key Learnings

Issue	Root Cause	Fix
`insufficient_scope` on all requests	`allowedClients` in gateway config; Auth0 uses `azp` not `client_id`	Use only `allowedAudience`
`authorizationCode must not be null`	Auth0 skips consent for first-party apps without permissions	Add API permission + disable consent skip
`Authorization error when sending message`	Lambda Function URL missing resource policy	`aws lambda add-permission` with `lambda:InvokeFunctionUrl`
`Invalid request` on consent URL	request_uri TTL expired (~60 seconds)	Open URL immediately after generation
Token never persists	Nothing calls `CompleteResourceTokenAuth`	Implement callback handler (this repo)

Auth0 Configuration Checklist

API created with custom identifier (audience)
At least one permission defined on the API
"Allow Skipping User Consent" is OFF
Post Login Action deployed (adds scp claim)
Application callback URLs include AgentCore callback URL
Application type: Regular Web Application
Token Endpoint Auth Method: client_secret_post

File Structure

.
├── README.md
├── requirements.txt
├── .env.example
├── .gitignore
├── app.py                          # Flask app (token endpoint + callback handler)
├── callback_handler.py             # Standalone callback handler example
├── lambda/
│   └── lambda_function.py          # Lambda MCP server (echo + whoami tools)
└── screenshots/
    ├── 3lo-sequence-diagram.png
    ├── 02-auth0-app-settings-callbacks.png
    ├── 04-auth0-api-settings-consent.png
    ├── 05-auth0-api-permissions.png
    ├── 08-agentcore-callback-received.png
    └── 09-auth0-login-flow-action.png

Cleanup

aws bedrock-agentcore-control delete-gateway-target \
  --gateway-identifier "<gateway-id>" --target-id "<target-id>" --region us-east-1

aws bedrock-agentcore-control delete-gateway \
  --gateway-identifier "<gateway-id>" --region us-east-1

aws bedrock-agentcore-control delete-oauth2-credential-provider \
  --name "auth0-3lo-example" --region us-east-1

aws lambda delete-function --function-name auth0-3lo-mcp-server --region us-east-1

Documentation

License

MIT

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maintenance

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Maintenance

–Maintainers

–Response time

–Release cycle

–Releases (12mo)

Commit activity

Resources

GitHub Repository

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