> For the complete documentation index, see [llms.txt](https://developer.dashdoc.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.dashdoc.com/docs/get-started/core-api-concepts.md).

# Core API concepts

- [Authentication](https://developer.dashdoc.com/docs/get-started/core-api-concepts/authentication.md)
- [External identifiers](https://developer.dashdoc.com/docs/get-started/core-api-concepts/external-identifiers.md)
- [Date and time formats](https://developer.dashdoc.com/docs/get-started/core-api-concepts/date-format.md)
- [Requests and filters](https://developer.dashdoc.com/docs/get-started/core-api-concepts/requests.md)
- [Pagination](https://developer.dashdoc.com/docs/get-started/core-api-concepts/pagination.md)
- [HTTP status codes](https://developer.dashdoc.com/docs/get-started/core-api-concepts/http-status-codes.md)
- [Rate limiting](https://developer.dashdoc.com/docs/get-started/core-api-concepts/http-status-codes-1.md)
- [Send documents](https://developer.dashdoc.com/docs/get-started/core-api-concepts/send-documents.md)