Apideck Accounting API + MCP vs Pennylane

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.

Pennylane

The v2 API has per-resource read and write scopes, an OpenAPI definition on every reference page, llms.txt and a breaking-change process that ran over 24 weeks. Access needs a paid Essentiel plan or partner approval, creation endpoints are not idempotent, and the API agreement lets Pennylane change or revoke the API without notice.

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

Pennylane

1. Call GET https://app.pennylane.com/api/external/v2/me first to confirm the token, user and company context
2. Stay under 25 requests per 5 seconds per token and wait for the retry-after value on a 429
3. Do not retry a create after a timeout without checking first. Only supplier invoice imports are deduplicated
4. Send filter and sort again with every cursor. The cursor stores position only
5. Send amounts as strings such as "120.00", and ask for :readonly scopes when the task only reads
6. Use the MCP server for reads only. It cannot create, edit or delete, and firm connections need company_id