Reference

Errors and limits

Error codes

Over MCP, an error comes back as a tool result with isError: true and the JSON below, so the agent can read it and recover. Over REST it's the response body, with the HTTP status.

Code	HTTP	Meaning
`invalid_input`	400	The input doesn't match the schema, or a value isn't allowed (an unknown stage or custom field). The message says which.
`unauthorized`	401	No valid token or key. Reconnect, or check the key.
`payment_required`	402	The workspace has no active subscription, so it's read-only. Reading and exporting still work.
`forbidden`	403	The connection's scopes don't allow this, or it's a people-only action.
`not_found`	404	No such record in this workspace.
`conflict`	409	The change clashes with existing data (a duplicate domain on another company, say).
`rate_limited`	429	Too many calls; the hint says when to retry.

{ "error": { "code": "invalid_input", "message": "…", "hint": "…" } }

Unexpected server errors return internal without details; they are logged and retrying may help.

Limits

Tool inputs have per-field limits (for example, a task title is at most 200 characters, a signal's why-now at most 280); each tool's page lists them.
List tools page with limit (usually up to 100) and next_cursor.
CSV imports take up to 10,000 rows per file.
Workspaces provided through a partner plan (such as the Founder Kit) have plan limits: 25,000 people, 10,000 companies, 3 members, 60 agent calls a minute and 20,000 a day per connection, and 12 months of change history.

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