Apideck Accounting API + MCP vs FreeAgent API

Apideck Accounting API + MCP

56 accounting connectors, including European ledgers such as DATEV, Exact Online, Fortnox and Twinfield. No published rate limits of Apideck's own, only connector limits mirrored in headers.

FreeAgent API

Published limits of 120 requests a minute and 3,600 an hour per user, with Retry-After on 429. No OAuth scopes, so a token can do anything the authorising user can.

Apideck Accounting API + MCP

1. Stay in dynamic mode and search for tools. Static mode loads all 362 schemas
2. Start the MCP with --lock-identity (or ?lock_identity=true) when one agent serves one customer
3. Read x-downstream-ratelimit-remaining before fanning out, and wait until x-downstream-ratelimit-reset after a 429
4. List before you retry a create that timed out. Writes aren't idempotent and there's no idempotency key
5. Pass fields= on list calls to cut the response to the columns you need

FreeAgent API

1. Store the new refresh token from every refresh response. The old one stops working
2. Create the invoice, then PUT /v2/invoices/:id/transitions/mark_as_sent. A draft isn't visible to the customer
3. Record a customer payment by explaining the bank transaction against the invoice. There's no invoice payments endpoint
4. Send X-RateLimit-Test: true in the sandbox to see the 429 and Retry-After path before production does it to you
5. Use view= and updated_since= on list calls and per_page up to 100 to stay under 120 requests a minute