Invoke a tool by name with a JSON body of its arguments. Runs the exact tool MCP would; acting (acts=true) tools require Infrastructure over REST.

Tool name from GET /tools.

Identifies an automation-platform integration (the official n8n node sends n8n, the Make app sends make). When set, every call, including a connection test against /me, requires a paid plan or a trial (reads work on any of them; acting tools still need Infrastructure), else 402 AUTOMATION_NOT_ENTITLED. Omit it for plain REST usage.

Makes the call safe to repeat (a UUID per logical call). The first request runs the tool; a repeat with the same key and arguments returns that run's response (header Idempotent-Replayed: true) or 409 IDEMPOTENCY_IN_PROGRESS while it still runs, and an ACTING tool (acts=true) is never run twice. Kept: acting calls for 24h; any call that outlived the 60s response (504 TOOL_TIMEOUT) for 24h if acting, 1h if a read. A fast read is not kept, so repeating it runs it again (harmless). Answers over 64 KB are returned once and not kept: a repeat gets 409 IDEMPOTENCY_RESULT_NOT_KEPT. Calls refused before running (400, 402, 403, 404, 429) are not kept, and neither is an acting call the tool refused for credits, a rate limit or a provider outage (402, 429, 503; nothing acted), so the key works again once fixed.