Fannie Mae MCP

A remote MCP server exposing Fannie Mae's public APIs, starting with the Loan Limits API. Uses OAuth2 client-credentials against Fannie Mae's PingOne authorization server -- no user-facing OAuth flow needed, just a client ID and secret from the Developer Portal.

Tools exposed:

• list_apis — catalog of all 16 public APIs (only Loan Limits is wired to live data so far)
• get_all_loan_limits — loan limits for every US county/territory
• get_historical_loan_limits — loan limits for a given calendar year (2009-2019)
• get_loan_limits_by_county — loan limits for one specific state + county

1. Prerequisites

• A Fannie Mae Developer Portal account with an approved app for the Loan Limits API (Public APIs category)
• Your app's client ID and client secret
• The token endpoint URL shown on the portal's "Create Access Token" step (PingOne URL specific to your app)
• A Vercel account

2. Push to GitHub

git init
git add .
git commit -m "Initial commit"
git remote add origin git@github.com:<you>/fannie-mae-mcp.git
git push -u origin main

3. Import into Vercel

1. Go to vercel.com/new → Import Git Repository → select this repo
2. In Environment Variables, add FANNIE_CLIENT_ID, FANNIE_CLIENT_SECRET, and FANNIE_TOKEN_URL
3. Click Deploy

Every future git push to main auto-deploys.

4. Connect it to Claude / Cowork

Add a custom connector pointing at:

https://<your-vercel-domain>/api/mcp

Then try: "List the Fannie Mae APIs available, then get loan limits for Los Angeles County, CA."

Local development

npm install
cp .env.example .env.local   # fill in your credentials
npm run dev

Notes

• Access tokens expire after 1 hour and are cached in memory per warm serverless instance; a cold start just fetches a fresh one automatically.
• Only Loan Limits is implemented so far. The other 15 catalog entries in list_apis are for browsing/reference -- extending to a new API means pulling its own Swagger docs first (base path, params, response shape) before wiring it up, the same way Loan Limits was built.