What is a REST API? A Plain-English Guide
REST API (Representational State Transfer) is the most widely adopted standard for building web service interfaces. Learn how REST APIs work, when to use them, and how they power enterprise integrations.
What is REST API?
A REST API (Representational State Transfer Application Programming Interface) is a standard architectural style for designing web services. REST APIs expose resources — users, orders, products — as URLs and let clients interact with those resources using standard HTTP methods: GET to retrieve data, POST to create, PUT or PATCH to update, and DELETE to remove. Each request is stateless, meaning the server holds no session memory between calls — every request carries all the information needed to process it.
- Uses standard HTTP methods: GET, POST, PUT, PATCH, DELETE
- Stateless: every request is self-contained, no server-side session
- Resources identified by unique URLs (endpoints)
- Responses are typically JSON; XML is also valid
- The most widely adopted API style for web and enterprise services
How REST API Works
A REST API works by mapping operations to HTTP verbs and resources to URL paths. The client sends an HTTP request to a specific endpoint with optional headers, a body, and auth credentials. The server validates the request, executes the operation, and returns an HTTP response with a status code and usually a JSON body.
Define resources as URLs
Each entity — user, order, product — gets a canonical URL. For example, /users/123 refers to user 123. Collections live at /users.
Assign HTTP verbs
GET retrieves, POST creates, PUT replaces, PATCH partially updates, DELETE removes. The same URL can support multiple verbs with different meanings.
Send the request
The client includes headers (Content-Type, Authorization), an optional JSON body, and calls the endpoint. TLS encrypts the connection.
Receive the response
The server returns an HTTP status code (200 OK, 201 Created, 400 Bad Request, 404 Not Found, 500 Server Error) and a JSON body with the result or error details.
Common REST API Use Cases
E-commerce integrations
A Shopify storefront calls a REST API to pull inventory from an ERP and push orders for fulfillment — keeping stock levels accurate in real time.
Mobile app backends
A React Native app fetches user profiles, posts updates, and retrieves notifications through REST endpoints backed by an API gateway.
Agentic workflow actions
AI agents in FlowGenX invoke REST API endpoints as discrete tools — querying a CRM, updating a ticket, or triggering a downstream service inside a multi-step workflow.
REST API in FlowGenX AI
FlowGenX's Integration Studio supports REST API connectors natively. You can import any OpenAPI/Swagger spec or Postman collection and auto-convert it into a fully managed, MCP-ready tool. Every REST endpoint becomes an action your AI agents can invoke in agentic workflows — with built-in OAuth2/API key auth, retry logic, rate-limit handling, and immutable audit trails. No custom connector code needed.
Frequently Asked Questions
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