# Core Concepts This page orients you to the cross cutting rules that apply to every Bead API. Each topic has its own detail page. The summaries below tell you when to click through. ### **Environments and base URLs** Sandbox and production hosts, ports, TLS requirements, health check endpoints, and how to switch between environments without code changes. See the Environments & Base URLs page in the Reference Guide for the full table of: * REST API base URLs for Sandbox and Production * OAuth token URLs for each realm (`nonprod` and `prod`) * Health check endpoints and connectivity notes ### **Authentication and OAuth 2.0** How to obtain and refresh access tokens for the Bead APIs. The Authentication page covers: * OAuth 2 password grant flow * Realms used by Bead (`nonprod` for Sandbox and other non production environments, `prod` for Production) * Which client to use (`bead-terminal` for Payments, `bead-integrator` for Onboarding and Entity Management) * Token response fields, expiry, and refresh token usage * Example curl requests and common error conditions Use this when you are wiring up token acquisition or troubleshooting authorization failures. ### **Error codes** Standard error response format and how to decide when to retry versus fail fast. The Error Codes page describes: * The standard JSON error object shape * How HTTP status codes map to fault categories * Which errors are safe to retry, such as transient `5xx` and `429` with backoff * Examples of validation errors (`400`), authentication issues (`401` or `403`), and not found conditions (`404`) Use this when building error handling, logging, and alerting for your integration. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://developers.bead.xyz/reference-guide/core-concepts.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.