AI Agents

Let Your AI Agent Answer Mortgage Questions with Real Data

Function calling integration for LLMs and native MCP server for Claude. Give your conversational AI access to live mortgage rates from 4,300+ credit unions.

MCP Setup GuideAPI Documentation
Last updated: January 27, 2026
Quick Answer

What is a Mortgage Rate API for AI Agents?

A mortgage rate API for AI agents provides function calling access to live mortgage rates from 4,300+ credit unions. Instead of hallucinating outdated rates, AI agents can query the API and respond with accurate, current information. RateAPI provides native MCP integration for Claude and OpenAPI schemas for GPT-4, Gemini, and other LLMs.

The Problem

AI Agents Hallucinate Rates or Punt to "Check with a Lender"

Ask ChatGPT, Claude, or any LLM about current mortgage rates and you'll get one of two responses: hallucinated numbers from training data (6 months to 2 years out of date), or a vague "I recommend checking with a mortgage lender for current rates."

Neither answer helps users. In a market where rates change weekly and a 0.5% difference means tens of thousands of dollars over the loan's life, stale data is worse than no data.

Your AI agent can do better. With RateAPI, your agent calls a function, gets live rates, and responds with accurate, actionable information in the same conversational turn.

And unlike rate comparison sites that rank by who paid more, your agent accesses unbiased data ranked by true cost—APR, points, fees, and lender reliability. The lowest advertised rate doesn't always win.

Integration

Two Ways to Connect

🤖

Claude MCP Server

Zero integration code

Install our MCP server and Claude Desktop or Claude Code can immediately query mortgage rates. No custom code, no function schemas to define. Just add the server and start asking.

$bash
# Add to Claude Code
claude mcp add rateapi \
  https://mcp.rateapi.dev/mcp \
  --transport http \
  --header "x-api-key: YOUR_KEY"
🛠

Function Calling API

Works with any LLM

Use our OpenAPI spec to generate tool schemas for GPT-4, Claude, Gemini, or any model with function calling. Standard REST endpoints optimized for LLM consumption.

{}json
// OpenAI function call response
{
  "name": "get_mortgage_rates",
  "arguments": {
    "state": "CA",
    "amount": 500000
  }
}
Features

Built for AI Integration

🔌

Native Function Calling Support

Endpoints return structured JSON optimized for LLM consumption. Every field is named for clarity, every response includes context.

🎯

MCP Server for Claude

Install and start asking. The MCP server handles tool registration, authentication, and response formatting automatically.

💬

Context-Aware Recommendations

Query by user context—state, loan amount, intent. The API returns recommendations your agent can explain conversationally.

🔔

Webhook for Proactive Agents

Set up monitors and receive webhooks when rates drop. Your agent can initiate conversations proactively.

⚖

Unbiased Ranking by True Cost

Rates ranked by APR, points, and fees—not by who paid for placement. Your agent recommends the genuinely best offer, not the highest bidder.

Examples

Conversations Your Agent Can Handle

Rate Comparison Query
U
User

I got a quote for 6.5% on a $400k mortgage in Texas. Is that any good?

AI
Agent

Your quote is above market—it ranks 847th out of 1,203 Texas lenders I analyzed. The top-ranked offer is 5.875% from Navy Federal Credit Union, which would save you $147/month or $52,920 over the loan. This offer ranks #1 not just because of the rate, but because it has zero points and reliable data—we filter out teaser rates that disappear when you actually apply. Would you like me to find credit unions you might qualify for?

Refinance Timing
U
User

My current mortgage is 7.25%. Should I refinance now or wait?

AI
Agent

Based on current rates, refinancing looks favorable. The top-ranked offer in your state is 5.99%—that's 1.26% below your current rate. On a typical $350k balance, you'd save around $290/month. I rank by total cost including APR and fees, not just the advertised rate, so this is the real deal. Even accounting for closing costs, the break-even is under 18 months. Want me to set up an alert if rates drop further?

Resources

Developer Resources

📄

OpenAPI Spec

Full API reference with schemas for tool generation

🤖

MCP Setup Guide

Step-by-step Claude Desktop and Claude Code integration

💻

Example Prompts

Sample system prompts and tool definitions

Try the MCP Server Now

If you're using Claude Desktop or Claude Code, add our MCP server and start asking mortgage questions immediately. The setup takes under a minute.

MCP Setup GuideMCP Server Docs
FAQ

Frequently Asked Questions

How do AI agents access mortgage rates?

AI agents access mortgage rates through RateAPI using either function calling (for GPT-4, Gemini, and other LLMs) or native MCP integration (for Claude). The API returns structured JSON with live rates from 4,300+ credit unions, which the agent can use to provide accurate, current information.

What is MCP (Model Context Protocol)?

MCP (Model Context Protocol) is Anthropic's open standard for connecting AI assistants to external tools and data sources. RateAPI provides a native MCP server that allows Claude Desktop and Claude Code to query mortgage rates directly without any custom integration code. Just add the server and start asking questions.

Can I use RateAPI with ChatGPT?

Yes, RateAPI works with ChatGPT and GPT-4 through OpenAI's function calling feature. Use our OpenAPI specification to generate tool schemas, then define the get_mortgage_rates function in your assistant. The API returns structured JSON that GPT-4 can interpret and present conversationally.

How accurate is the rate data?

RateAPI scrapes rates directly from 4,300+ credit union websites daily. Rates are typically updated within 24 hours of changes. Unlike rate comparison sites, we don't accept paid placements or rank by advertising spend. Rates are ranked by true cost including APR, points, and fees.

Is there a free tier for AI agents?

Yes, RateAPI offers a free tier with 20 requests per month (or 50 with email registration). This is perfect for testing your AI agent integration. Paid plans start at $29/month for higher volumes and additional features like webhooks and rate monitoring.

Ready to Give Your AI Real Mortgage Data?

Get your API key in seconds. Free tier includes 20 requests/month (or 50 with email). Perfect for testing your agent integration.

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