Arca Savings Rates API

A read-only API of U.S. savings rates from the banks and fintechs Arca tracks. Every rate is the APY (annual percentage yield) on a $10,000 balance, published only after the account's conditions are verified. Rate change history covers Arca's weekly checks since May 2026.

Access is by partnership. Contact Arca at alex@arcasavings.com.

• OpenAPI document: every operation, field and example.
• How Arca checks rates.

Setup

Send your key in the X-Arca-Key header on every request. Base URL: https://arcasavings.com/api/v1. Responses are JSON. The OpenAPI document needs no key.

Tools

Every tool is Read. None is a write or a sensitive write. None changes data, an account or a permission, and none acts for the user.

• getSummary (GET /summary): Read. No side effects.
• getAccounts (GET /accounts): Read. No side effects.
• getRateChanges (GET /rate-changes): Read. No side effects.
• calculateInterest (POST /calculate/interest): Read. Arithmetic only. POST carries the numbers in the body. Inputs are not stored, logged or cached.
• calculateGoal (POST /calculate/goal): Read. Arithmetic only, as above.

No user account, sign-in or personal data is involved. Nothing is pending or asynchronous: every response is final.

Errors

Errors return { "error": { "code", "message" } }. The message names the field and never repeats a value sent.

• 400 bad_request: a missing or invalid parameter.
• 401 unauthorized: a missing or unknown key.
• 429: more than 600 requests a minute. Wait a minute and retry.
• 500 internal: retry once. Every tool is safe to retry.

Changelog

Newest first.

• November 6, 2026: Version 1.0.2. The OpenAPI document now states its license (info.license): the Arca Savings Terms of Use. No change to any request or response.
• November 4, 2026: Version 1.0.1. The calculateInterest description now says to use it for any dollar amount of interest, including the yearly difference between two rates on a balance. No change to any request or response.
• November 3, 2026: Version 1.0.0, the first release. GET /summary, GET /accounts, GET /rate-changes (the newest 25 changes, with truncated), POST /calculate/interest and POST /calculate/goal. Partner key in the X-Arca-Key header; up to 600 requests a minute.

Arca provides information, not financial advice.