---
title: "RateAPI Developer Portal"
description: "The RateAPI developer portal: get a free API key, read the REST reference and OpenAPI spec, connect the MCP server, run against the sandbox, and set up webhooks."
canonical: "https://rateapi.dev/developers"
last-updated: "2026-08-21"
source: "https://rateapi.dev/llms.txt"
---

# Build on RateAPI

Live, evidence-backed interest rates from 3,700+ US credit unions, over a REST API and a 76-tool MCP server. Every resource you need is on this page. A key takes an email address and about ten seconds.

## RateAPI Quickstart

Three steps from nothing to a ranked list of real offers.

### Get an API key

Free tier, email required, no credit card. Pass `source` so we can tell where signups come from.

```
curl -X POST https://api.rateapi.dev/keys \
  -H "Content-Type: application/json" \
  -d '{"email":"you@example.com","source":"developer-portal"}'
```

### Make your first call

`POST /v1/decisions` takes a borrower’s situation and returns ranked offers with the savings math already done.

```
curl -X POST https://api.rateapi.dev/v1/decisions \
  -H "X-API-Key: rk_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{"state":"CA","intent":"purchase","amount":500000,"product_type":"mortgage"}'
```

### Read the rate-limit headers

Every response carries your remaining budget, so you can self-throttle instead of discovering the ceiling with a 429. See the table below.

```
RateLimit-Limit: 20
RateLimit-Remaining: 19
RateLimit-Reset: 2591940
RateLimit-Policy: 20;w=2592000
```

## Sandbox & keyless demo

Two ways to exercise the API before you commit to an integration.

### Keyless demo endpoint

`GET /v1/demo/rates` needs no key and no signup. It returns a small fixed sample of the live book in exactly the shape `/v1/rates` uses, so you can confirm the response contract before writing any auth code.

```
curl https://api.rateapi.dev/v1/demo/rates
```

### Sandbox keys

A key prefixed `rk_test_` routes every `/v1` endpoint to deterministic stub data. Nothing is metered and nothing is billed, so it is safe for CI and for demos. Ask us for one at [support@rateapi.dev](mailto:support@rateapi.dev).

## RateAPI documentation & reference

The REST surface, described both for people and for machines.

- [RateAPI API ReferenceEvery REST endpoint with request and response shapes, filters, and worked examples.api.rateapi.dev](https://api.rateapi.dev/)
- [RateAPI OpenAPI SpecificationThe full OpenAPI 3 document — 52 operations, typed parameters, response schemas, and documented rate-limit headers. Feed it straight to a code generator or an agent.api.rateapi.dev/openapi.json](https://api.rateapi.dev/openapi.json)
- [Capabilities CatalogMachine-readable, no key required: every flow RateAPI supports, paired with its REST route and its MCP tool.api.rateapi.dev/v1/capabilities](https://api.rateapi.dev/v1/capabilities)
- [Decision API ReferencePOST /v1/decisions — personalized, ranked offers with savings math. The endpoint most integrations start and stay on.rateapi.dev/api/reference](https://rateapi.dev/api/reference)
- [Rate Query APIGET /v1/rates — filter the live book by product, state, occupancy, term, and audience.rateapi.dev/rates-api](https://rateapi.dev/rates-api)
- [Eligibility APIWhich credit unions a person can actually join, with a verbatim evidence quote behind every verdict.rateapi.dev/api/eligibility](https://rateapi.dev/api/eligibility)

## RateAPI integrations

Everything past a plain HTTP call: agents, events, embeds, and the rules of the road.

- [RateAPI MCP Server76 Model Context Protocol tools over Streamable HTTP. Connect Claude, ChatGPT, or any MCP client to the live rate book.mcp.rateapi.dev/mcp](https://rateapi.dev/mcp)
- [WebhooksSubscribe to rate movements and monitor triggers; inspect and replay past deliveries.api.rateapi.dev/webhooks](https://api.rateapi.dev/webhooks)
- [Embeddable Rate WidgetsOne script tag puts live, sourced rates on any static page. No key, no build step.rateapi.dev/widget-docs](https://rateapi.dev/widget-docs)
- [Agent Skills GalleryReady-made recipes (SKILL.md + recipe.json) for rate shopping, affordability, refinance break-even, and monitoring.rateapi.dev/skills](https://rateapi.dev/skills)
- [IdempotencyHow to make writes safely retryable with the Idempotency-Key header.rateapi.dev/api/idempotency](https://rateapi.dev/api/idempotency)
- [Versioning & Deprecation PolicyHow RateAPI versions its API and how a breaking change is signalled before it lands.rateapi.dev/deprecation-policy](https://rateapi.dev/deprecation-policy)

## RateAPI for AI agents

Machine-readable orientation files. Fetch any of them directly; none require a key. Every RateAPI page also answers `Accept: text/markdown` with a markdown representation of itself.

- [llms.txtCompact orientation for an LLM: what RateAPI covers, what it uniquely answers, and how to call it.rateapi.dev/llms.txt](https://rateapi.dev/llms.txt)
- [llms-full.txtThe long form — full API documentation, methodology, coverage, and FAQ in one plain-text document.rateapi.dev/llms-full.txt](https://rateapi.dev/llms-full.txt)
- [Agent InstructionsWhen an agent should reach for RateAPI, which tool to pick per job, and the rules for quoting a rate.rateapi.dev/.well-known/agent-instructions.md](https://rateapi.dev/.well-known/agent-instructions.md)
- [MCP ManifestDiscovery document for MCP clients: server URL, transport, auth, and tool count.rateapi.dev/.well-known/mcp](https://rateapi.dev/.well-known/mcp)

## Rate limits

RateAPI returns the RFC 9331 `RateLimit-*` headers on every response, authenticated or not, alongside the legacy `X-RateLimit-*` pair. On a 429 you also get `Retry-After` in seconds.

| Header | Meaning |
| `RateLimit-Limit` | Requests allowed in the current window. |
| `RateLimit-Remaining` | Requests left in the current window. |
| `RateLimit-Reset` | Seconds until the window resets. |
| `RateLimit-Policy` | The quota and window, e.g. `20;w=2592000` for 20 requests per 30 days. |
| `Retry-After` | On a 429 only: seconds to wait before retrying. |

## Get a key

Free tier, no credit card. If you get stuck, write to [support@rateapi.dev](mailto:support@rateapi.dev) or see the [contact page](https://rateapi.dev/contact) — a person answers.

Generate a free API key

Developer Portal

⚡RateAPI

Daily-verified lending rates from 3,700+ US credit unions, plus deposit APY benchmarks for savings, CDs, share certificates, and money markets.

[Sign In →](https://app.rateapi.dev)

### Products

- [Current Rates →](https://rateapi.dev/current-mortgage-rates)
- [Current Auto Loan Rates](https://rateapi.dev/current-auto-loan-rates)
- [Current CD Rates](https://rateapi.dev/current-cd-rates)
- [Current HELOC Rates](https://rateapi.dev/current-heloc-rates)
- [Current Personal Loan Rates](https://rateapi.dev/current-personal-loan-rates)
- [Credit Union Rate Index](https://rateapi.dev/credit-union-rate-index)
- [For Credit Unions](https://rateapi.dev/for-credit-unions)
- [Mortgage Rates](https://rateapi.dev/mortgage-rates)
- [Auto Loan Rates](https://rateapi.dev/auto-loan-rates)
- [RV Loan Rates](https://rateapi.dev/rv-loan-rates)
- [Boat & Marine Rates](https://rateapi.dev/boat-loan-rates)
- [Motorcycle Rates](https://rateapi.dev/motorcycle-loan-rates)
- [HELOC Rates](https://rateapi.dev/heloc-rates)
- [Personal Loan Rates](https://rateapi.dev/personal-loan-rates)
- [Credit Card Rates](https://rateapi.dev/credit-card-rates)
- [Credit Union Directory →](https://rateapi.dev/credit-unions)

### Resources

- [Should I Refinance?](https://rateapi.dev/should-i-refinance)
- [When to Lock Your Rate](https://rateapi.dev/when-to-lock-your-rate)
- [Auto vs Personal Loan](https://rateapi.dev/auto-loan-vs-personal-loan)
- [Pricing →](https://rateapi.dev/pricing)
- [Use Cases](https://rateapi.dev/use-cases)
- [AI Integration](https://rateapi.dev/ai)
- [AI Guides →](https://rateapi.dev/ai-guides)
- [Mortgage Benchmark](https://rateapi.dev/mortgage-rate-benchmark)
- [Auto Loan Benchmark](https://rateapi.dev/auto-loan-rate-benchmark)
- [Data Methodology](https://rateapi.dev/methodology)
- [Transparency](https://rateapi.dev/transparency)
- [Datasets →](https://rateapi.dev/credit-union-rate-dataset)

### Company

- [About](https://rateapi.dev/about)
- [What is RateAPI?](https://rateapi.dev/what-is-rateapi)
- [Mortgage Rate API Guide](https://rateapi.dev/what-is-mortgage-rate-api)
- [Auto Loan Rate API Guide](https://rateapi.dev/what-is-auto-loan-rate-api)
- [FAQ](https://rateapi.dev/faq)
- [Independence](https://rateapi.dev/independence)
- [Corrections](https://rateapi.dev/corrections)
- [Contact](https://rateapi.dev/contact)
- Are you a real estate agent or lender?

### Developers

- [Developer Portal →](https://rateapi.dev/developers)
- [API Reference](https://api.rateapi.dev/)
- [OpenAPI Spec](https://api.rateapi.dev/openapi.json)
- [Webhooks](https://api.rateapi.dev/webhooks)
- [MCP Server](https://rateapi.dev/mcp)
- [Embed Widgets](https://rateapi.dev/widget-docs)
- [Versioning & Deprecation](https://rateapi.dev/deprecation-policy)
- [GitHub](https://github.com/rate-api)

© 2026 RateAPI | [llms.txt](https://rateapi.dev/llms.txt)

---

Source: https://rateapi.dev/developers
Rate data API: https://api.rateapi.dev · OpenAPI: https://api.rateapi.dev/openapi.json · MCP: https://mcp.rateapi.dev/mcp