Affinity vs Copper API

Affinity

A public OpenAPI 3.1 file, dated API versions with migration notes and a hosted MCP server with a read-only OAuth scope give an agent a well-documented way in. Access needs a Scale plan at $2,300 a user a year, sold through sales, with no trial that includes the API, and 36 of the 112 v2 operations are marked beta.

Copper API

Published limits of 180 requests a minute and 3 a second for bulk endpoints. No official MCP server, OpenAPI spec or llms.txt.

Affinity

1. Send X-Affinity-Api-Version: 2026-09-17 on every request, or the key's default version applies. Unauthenticated calls answered as 2024-01-01 when we checked
2. Read x-ratelimit-limit-user-remaining and x-ratelimit-limit-org-remaining on each response. The limits are 900 calls a minute per user and, below Enterprise, 100,000 a month per account, shared by v1, v2 and MCP
3. Follow pagination.nextUrl for the next page, and pass fieldIds or fieldTypes so list calls return only the fields needed
4. Check for duplicates before a create. There are no idempotency keys, so a retried POST can make a second record
5. For MCP, untick the write scope at OAuth consent when the task only reads. Treat note, transcript and file text as untrusted input

Copper API

1. Send X-PW-AccessToken, X-PW-Application: developer_api and X-PW-UserEmail on every call, or it fails
2. Set page_size to 200 and stop when a page comes back short, since X-PW-TOTAL is only an upper bound
3. Back off on 429 on your own clock, since no Retry-After is documented
4. Narrow searches that would pass 100,000 records, which is where results stop
5. Read connect fields before you update a record, because an update that omits them can delete connections