Add Okta OAuth to a Calculator MCP Server

Learn how to create and deploy an OAuth2-authenticated MCP server using Okta and FastMCP, then integrate it with TrueFoundry AI Gateway.

This guide demonstrates how to write an MCP server, add Oauth based authentication to it using Okta as the identity provider, and then integrate it with the TrueFoundry AI Gateway. The setup below explains both the user authentication and machine-to-machine authentication scenarios:

• User Authentication: Authenticate specific users through the AI Gateway using the Authorization Code flow with refresh tokens
• Machine-to-Machine Authentication: Enable programmatic access without user interaction using the Client Credentials grant flow

The entire code for the steps described below can be found in this Github link: https://github.com/truefoundry/getting-started-examples/tree/main/calculator-oauth-mcp-server

Guide to creating the MCP server and adding Oauth

1. Write a basic MCP Server and test it locally

   Let’s start by writing a basic MCP server that provides a get_me tool.

   server.py

   from fastmcp import FastMCP
   
   mcp = FastMCP("Demo 🚀")
   
   @mcp.tool
   def add(a: int, b: int) -> int:
       """Add two numbers"""
       return a + b
   
   @mcp.tool
   def subtract(a: int, b: int) -> int:
       """Subtract two numbers"""
       return a - b
   
   if __name__ == "__main__":
       mcp.run(transport="streamable-http", stateless_http=True)
   

   Run the server locally:

   python server.py
   

   Your MCP server will be available at http://localhost:8000/mcp. Test the server using this Python script:

   test.py

   import asyncio
   from fastmcp import Client
   
   async def main():
       async with Client("http://127.0.0.1:8000/mcp") as client:
           tools = await client.list_tools()
           print(tools)
           result = await client.call_tool(
               name="add", 
               arguments={"a": 1, "b": 2}
           )
           print(result)
   
   asyncio.run(main())
   

   This MCP server is running without any authentication. Enable OAuth next by registering the server in Okta, then adding JWT verification to the code.

2. Register the MCP server in Okta

   Create an authorization server, OAuth app, access policy, and scopes in Okta. Follow Okta app setup and collect:

   • OAUTH_ISSUER and OAUTH_JWKS_URI (from the authorization server)
   • OAUTH_AUDIENCE
   • CLIENT_ID and CLIENT_SECRET (for TrueFoundry; the MCP server itself only needs issuer, JWKS, and audience to verify tokens)
3. Modify MCP server code to add Oauth Token verification

   Create a .env file to add the environment variables and modify the server.py file to add the JWT verification.

   server.py

   from fastmcp import FastMCP
   import os
   from fastmcp.server.auth.providers.jwt import JWTVerifier
   from dotenv import load_dotenv
   
   load_dotenv()
   
   # Configure JWT verification using JWKS
   token_verifier = JWTVerifier(
       jwks_uri=os.getenv("OAUTH_JWKS_URI"),
       issuer=os.getenv("OAUTH_ISSUER"),
       audience=os.getenv("OAUTH_AUDIENCE"),
   )
   
   # Bearer token authentication
   mcp = FastMCP("Demo 🚀", auth=token_verifier)
   
   # Forward .well-known/oauth-authorization-server to the actual OAuth server
   @mcp.custom_route("/.well-known/oauth-authorization-server", methods=["GET", "HEAD", "OPTIONS"], include_in_schema=False)
   async def oauth_well_known(request: Request):
       """Redirect to the upstream OAuth server's well-known endpoint."""
       return RedirectResponse(os.environ.get(f"OAUTH_ISSUER") + "/.well-known/oauth-authorization-server", status_code=307)
   
   @mcp.tool
   def add(a: int, b: int) -> int:
       """Add two numbers"""
       return a + b
   
   @mcp.tool
   def subtract(a: int, b: int) -> int:
       """Subtract two numbers"""
       return a - b
   
   if __name__ == "__main__":
       mcp.run(transport="streamable-http", host="0.0.0.0", port=8000, stateless_http=True)
   

4. Get the token and call the MCP server in test.py (Machine-to-Machine authentication)

   In Step 1, we had a script to test the MCP server locally. After adding the Oauth token verification to the MCP server in the previous step, we need to modify the script to get the token and then call the MCP server. If you call the MCP server without a token, it will return a 401 Unauthorized error.

   test.py

   import asyncio
   from fastmcp import Client
   import requests
   import base64
   
   # Configuration
   TOKEN_ENDPOINT = "https://example.okta.com/oauth2/ksdhflsdjfla/v1/token"
   M2M_CLIENT_ID = "klasjflsdjsd"
   M2M_CLIENT_SECRET = "xxx-xxx-xxx"
   AUDIENCE = "https://calculator-mcp-server.example.com"
   
   # Encode credentials
   credentials = base64.b64encode(f"{M2M_CLIENT_ID}:{M2M_CLIENT_SECRET}".encode()).decode()
   
   # Request token
   response = requests.post(
       TOKEN_ENDPOINT,
       headers={
           "Authorization": f"Basic {credentials}",
           "Content-Type": "application/x-www-form-urlencoded"
       },
       data={
           "grant_type": "client_credentials",
           "audience": AUDIENCE,
           "scope": "calculator.add"
       }
   )
   
   print(response.json())
   response.raise_for_status()
   token_data = response.json()
   access_token = token_data["access_token"]
   
   print(f"Access Token: {access_token}")
   print(f"Expires in: {token_data['expires_in']} seconds")
   
   # Call the MCP server
   async def main():
       async with Client("https://calculator-mcp-abhay-8000.tfy-usea1-ctl.devtest.truefoundry.tech/mcp", auth=access_token) as client:
           tools = await client.list_tools()
           print(tools)
           result = await client.call_tool(
               name="add", 
               arguments={"a": 1, "b": 2}
           )
           print(result)
   
   asyncio.run(main())
   

   The test.py script above contains the code to get the Okta token and then call the MCP server.

   The OAUTH_WELL_KNOWN_URL enables the MCP server to expose the /.well-known/oauth-authorization-server endpoint, which allows the AI Gateway to auto-discover OAuth configuration details. This endpoint redirects to your Okta authorization server’s well-known endpoint.

   This is exactly how you will be doing Machine-to-Machine authentication to the MCP server. Code snippets to get the token in different ways are outlined below:

   Using cURL

   # Set your values
   TOKEN_ENDPOINT="https://dev-12345678.okta.com/oauth2/aus123abc/v1/token"
   M2M_CLIENT_ID="0oa123abc..."
   M2M_CLIENT_SECRET="secret123..."
   AUDIENCE="https://your-mcp-server.example.com"
   
   # Encode client credentials
   CREDENTIALS=$(echo -n "${M2M_CLIENT_ID}:${M2M_CLIENT_SECRET}" | base64)
   
   # Request access token
   curl -X POST "${TOKEN_ENDPOINT}" \
     -H "Authorization: Basic ${CREDENTIALS}" \
     -H "Content-Type: application/x-www-form-urlencoded" \
     -d "grant_type=client_credentials" \
     -d "scope=my_custom_scope" \
     -d "audience=${AUDIENCE}"
   

   Response:

   {
     "access_token": "eyJraWQiOiJxMmFt...",
     "token_type": "Bearer",
     "expires_in": 3600,
     "scope": "my_custom_scope"
   }
   

   When using a custom authorization server, you can use custom scopes defined in your authorization server. Make sure to include the audience parameter matching the audience configured in your authorization server.

   Using Python

   import requests
   import base64
   
   # Configuration
   TOKEN_ENDPOINT = "https://dev-12345678.okta.com/oauth2/aus123abc/v1/token"
   M2M_CLIENT_ID = "0oa123abc..."
   M2M_CLIENT_SECRET = "secret123..."
   AUDIENCE = "https://your-mcp-server.example.com"
   
   # Encode credentials
   credentials = base64.b64encode(f"{M2M_CLIENT_ID}:{M2M_CLIENT_SECRET}".encode()).decode()
   
   # Request token
   response = requests.post(
       TOKEN_ENDPOINT,
       headers={
           "Authorization": f"Basic {credentials}",
           "Content-Type": "application/x-www-form-urlencoded"
       },
       data={
           "grant_type": "client_credentials",
           "scope": "my_custom_scope",
           "audience": AUDIENCE
       }
   )
   
   response.raise_for_status()
   token_data = response.json()
   access_token = token_data["access_token"]
   
   print(f"Access Token: {access_token}")
   print(f"Expires in: {token_data['expires_in']} seconds")
   

   Using Python with requests-oauthlib

   from oauthlib.oauth2 import BackendApplicationClient
   from requests_oauthlib import OAuth2Session
   
   # Configuration
   TOKEN_ENDPOINT = "https://dev-12345678.okta.com/oauth2/aus123abc/v1/token"
   M2M_CLIENT_ID = "0oa123abc..."
   M2M_CLIENT_SECRET = "secret123..."
   
   # Create OAuth2 session
   client = BackendApplicationClient(client_id=M2M_CLIENT_ID)
   oauth = OAuth2Session(client=client)
   
   # Fetch token
   token = oauth.fetch_token(
       token_url=TOKEN_ENDPOINT,
       client_id=M2M_CLIENT_ID,
       client_secret=M2M_CLIENT_SECRET,
       scope=["my_custom_scope"]
   )
   
   access_token = token["access_token"]
   print(f"Access Token: {access_token}")
   
5. Host the MCP server and get the endpoint URL

   Now that we have tested the MCP server locally, we will add it to the AI Gateway to enable user authentication and allow the MCP server to be accessed via the AI Gateway. To add the MCP server to the AI Gateway, we need to get the endpoint URL of the MCP server. Hence, we need to host the MCP server on a public URL.

   If you are using the TrueFoundry AI Deployment product, this can be done by creating a service deployment, choosing your Github repository containing the MCP server code above. Otherwise, you can host it on a VM or a Kubernetes cluster or any hosting provider of your choice.

   Remember to add the environment variables for the MCP server:

   Variable	Value	Description
   OAUTH_JWKS_URI	https://dev-12345678.okta.com/oauth2/aus123abc/v1/keys	JSON Web Key Set URI for token verification
   OAUTH_ISSUER	https://dev-12345678.okta.com/oauth2/aus123abc	Authorization server issuer URI
   OAUTH_AUDIENCE	https://your-mcp-server.example.com	Audience identifier for your API

   The MCP server only needs these environment variables to validate OAuth tokens. It doesn’t need the Client ID or Client Secret since it’s only validating tokens, not generating them.

   After deployment, you will have the endpoint URL of the MCP server. Let’s consider it https://calculator-oauth-mcp-server.example.com for the rest of the steps. After deploying, check once using the test.py script above by changing the MCP server URL to the deployed URL. You should be able to fetch the tools from the MCP server.

6. Add the MCP server to the TrueFoundry AI Gateway

   You will need to have a MCP server group to be able to add the MCP server to the TrueFoundry AI Gateway. Please refer to the Getting Started guide to create a MCP server group.

   1. In your MCP Server Group, click Add MCP Server

   2. Select Remote MCP

   3. Configure the server:

      • Name: oauth-mcp-server
      • Description: OAuth-authenticated MCP server with Okta
      • URL: Your deployed service endpoint (e.g., https://calculator-oauth-mcp-server.example.com/mcp).
      • Transport: streamable-http
      • Authentication Type: Select OAuth2

   4. In the OAuth2 configuration section, provide the Okta credentials:

      • OAuth2 Client ID: Your Okta application client ID
      • OAuth2 Client Secret: Your Okta application client secret

   The AI Gateway will automatically discover the OAuth2 Authorization URL, Token URL, and other configuration details from your MCP server’s /.well-known/oauth-authorization-server endpoint once you provide the MCP server URL.

   You can optionally configure:

   • OAuth2 Scopes: The scopes are prefilled, but you can change them if needed to use your custom scopes.
   • Include offline_access in the scopes to enable refresh tokens. This allows the AI Gateway to automatically refresh expired access tokens without requiring users to re-authenticate.
   • You can store the client id and secrets in truefoundry secrets and reference them by FQN in the configuration.

   5. Set access control: Select teams or users who should have access to this MCP server.

   Managers of the MCP Server Group automatically have access to all servers in the group.

   

   6. Click Save to add the MCP server
      • The server will appear in your MCP Server Group
      • Users can now connect and use the server through the AI Gateway
7. Test the MCP server in the Playground

   1. Navigate to the Playground in the AI Gateway.
   2. Click Add Tool/MCP Servers
   3. Find your calculator-oauth-mcp-server in the list
   4. Click Connect Now to initiate OAuth authorization

   

   5. You’ll be redirected to Okta to authorize access
   6. Click Allow to grant access
   7. You’ll be redirected back to the AI Gateway
   8. The AI Gateway will store your OAuth tokens securely and refresh them automatically when they expire
   9. You’ll see the add and subtract tools from your MCP server
   10. Select the tools and click Done
   11. Try sending a prompt like Add 1 and 2. Use the tools provided
   12. The tool will return the result from your MCP server

   

Okta setup for On-Behalf-Of (OBO) token exchange

For Okta authorization servers, native app, API Services app, Token Exchange grant, and the manual curl check, see Okta app setup. Gateway-side manifests and troubleshooting are in Scenario 7: Okta OBO Token Exchange.