Conventions

Requests

• Base URL: https://app.commitly.com/api. All paths end with a slash; without it, the API answers with a redirect and the request body is lost.
• JSON in, JSON out. Amounts are decimals with two places; send them as numbers. Dates are YYYY-MM-DD.
• Negative amounts are outflows, positive amounts inflows.
• Bulk calls: several endpoints accept a JSON array, for example to create transactions or change their categories (up to 1,000 items per call).

Pagination

Lists of banks, transactions, invoices and budgets are paginated:

{ "count": 3063, "next": "…?page=2", "previous": null, "results": [ … ] }

• page and page_size (default 100, maximum 1,000).
• For invoices and budgets, results is an object with the list inside (invoices or budgets) plus totals.
• Categories and plans come as a plain list without pagination.
• Always call https://app.commitly.com/api. If a next link points to another host, take only the page number from it.

Errors

Status	Meaning	Body
400	Validation failed	{"field": ["message"]} or {"non_field_errors": ["message"]}; for arrays one object per item
401	Access token invalid or expired	{"detail": "Invalid token."}
403	No access token, or not allowed (for example a committed plan)	{"detail": "…"}
404	Not found	{"detail": "…"}
500	Server error	Not JSON

Language

Messages are German by default. Send Accept-Language: en (or de, it) to get them in another language. React to status codes and field names, not to message text.

Rate limits

Please avoid excessive request rates: cache the access token, use page_size instead of many small pages, and sync changes rather than full data sets where you can.