Copper API vs Nutshell

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.

Nutshell

The REST reference is served as Markdown with an OpenAPI fragment per operation, and the hosted MCP server uses OAuth with PKCE and can only read. No rate limit numbers, error format or API changelog were found in the reviewed documentation, and API keys carry no scopes.

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

Nutshell

1. Authenticate REST calls with HTTP Basic, a Nutshell user's email as username and the API key as password, against https://app.nutshell.com/rest
2. Use IDs in the <number>-<type> form, such as 3-accounts, and send updates as JSON Patch with content-type: application/json-patch+json
3. Page lists with page[limit] and page[page], which is 0-based, and call /accounts/list/fields or the lead and contact equivalents for valid filter keys
4. Use the REST API for writes. The MCP server only reads, and OAuth tokens need the read scope
5. Filter webhook events yourself, because every webhook receives all events and subscriptions are created in Setup, not through the API