Square APIs & SDKs: Build Custom Solutions on Square

# Square Developer Platform > Square APIs and SDKs for accepting payments, managing catalogs, running storefronts, and building on Square's point-of-sale ecosystem. Designed to be consumable by both human developers and AI agents. Square serves millions of merchants across restaurants, retail, appointments, and professional services. Our APIs cover payments, orders, catalog, inventory, customers, bookings, subscriptions, invoices, loyalty, gift cards, disputes, terminal hardware, and team/labor management. For agents: every write endpoint accepts an idempotency key; every list endpoint supports cursor-based pagination. Agent guidance: Use this file as the compact index for Square developer documentation. For full-document ingestion, fetch the [full documentation corpus](https://developer.squareup.com/llms-full.txt). To answer specific questions, fetch only the relevant API links from this index instead of loading the full corpus unless explicitly needed. ## Developer Essentials Learn about the Square Developer platform and how Square APIs and SDKs work together. ### Build basics Learn about design concepts and patterns for building applications with Square APIs. - [Authentication](https://developer.squareup.com/docs/auth): Learn about client application authentication using Square authentication APIs. - [Access Tokens](https://developer.squareup.com/docs/build-basics/access-tokens): Learn about the different Square access tokens and how to generate the correct token for your needs. - [Square API Lifecycle](https://developer.squareup.com/docs/build-basics/api-lifecycle): Learn about the Square API lifecycle and what to expect for each stage of development. - [Clear Object Fields](https://developer.squareup.com/docs/build-basics/clearing-fields): Learn how to clear Square API resource fields using a standard method for all clearable fields. - [Idempotency](https://developer.squareup.com/docs/build-basics/common-api-patterns/idempotency): Learn about idempotency a