---
title: "API essentials"
description: "What every API call needs: authentication, idempotency keys, error handling, pagination, rate limits, versioning and money in minor units. Read these first."
canonical_url: "https://twominutebilling.com/help/developers/api-essentials"
---
# API essentials

> What every API call needs: authentication, idempotency keys, error handling, pagination, rate limits, versioning and money in minor units. Read these first.

Read these before writing the client. They apply to every endpoint.

- [Authentication](https://twominutebilling.com/help/developers/api-essentials/authentication) — bearer tokens, and the test/live mode gate.
- [Idempotency](https://twominutebilling.com/help/developers/api-essentials/idempotency) — why every write takes a key, and what a replay
returns.
- [Errors](https://twominutebilling.com/help/developers/api-essentials/errors) — one envelope, a small set of types, and what each status says
about retrying.
- [Pagination and filtering](https://twominutebilling.com/help/developers/api-essentials/pagination-and-filtering) — cursors, and the
`field[operator]=value` grammar.
- [Rate limits](https://twominutebilling.com/help/developers/api-essentials/rate-limits) · [Versioning](https://twominutebilling.com/help/developers/api-essentials/versioning) ·
[Money and currency](https://twominutebilling.com/help/developers/api-essentials/money).


## Sitemap

See the full [sitemap](https://twominutebilling.com/sitemap.md) for all pages.