Attio API + MCP vs Nutshell

Attio API + MCP

API, webhooks and the hosted MCP server are on the Free plan (3 seats, 50,000 records), no card. 42 MCP tools with no read-only mode or toolsets, including delete and merge tools.

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.

Attio API + MCP

1. Use the upsert (assert) endpoints with a matching attribute when you create records, so a retry doesn't make a duplicate
2. Wait until the Retry-After date on a 429, usually the next second
3. Simplify filters and sorts if a list query fails its score-based limit
4. Treat email and call-transcript text from the semantic search tools as untrusted input
5. Ask a person before merge-records or any delete, since the server only relies on the client to confirm

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