A clean REST API names resources with plain nouns, uses HTTP methods consistently (GET to read, POST to create, PUT or PATCH to update, DELETE to remove), returns clear status codes and error messages, supports paging and filtering, is versioned, and is documented. These habits make integrations predictable for any developer who uses them.
- Design around resources such as customers and invoices, not around actions.
- Use standard HTTP methods and status codes so clients behave predictably.
- Plan for paging, filtering, versioning and safe retries from the start.
- Documentation and consistent errors save more time than any clever feature.
What makes an API RESTful in practice?
REST is a style for designing web APIs around resources, the things your business deals with, such as customers, orders and invoices. Each resource has an address, and clients use standard web operations on it. You do not need to follow every academic rule; the practical goal is that a developer can guess how your API behaves after seeing a few examples.
Consistency is the real test. If one endpoint returns dates as text and another as numbers, or one uses plural names and another singular, every integrator pays the cost. Agree conventions at the start and apply them everywhere, including to internal APIs that may become external later.
How should you name resources and use methods?
Use plural nouns for collections, such as /customers and /customers/123. Avoid verbs in the address, since the HTTP method already says what to do. GET reads, POST creates, PUT replaces, PATCH changes part of a record and DELETE removes. Nest only when ownership is clear, for example /customers/123/invoices.
Some actions do not fit neatly, such as cancelling an order or sending an invoice. Model them as a sub-resource or a clearly named action under the resource, and keep them rare. GET requests should never change data, because browsers, caches and crawlers assume they are safe to repeat.
- Plural nouns for collections and ids for single items
- GET never changes data
- POST creates; PATCH changes part of a record
- Same naming style for fields, such as one case convention throughout
- Dates in one standard format with a time zone
Which status codes and errors should you return?
Use the status code to tell the client what happened: success codes in the 200 range, client mistakes in the 400 range, and server problems in the 500 range. A missing record is 404, bad input is 400 or 422, lack of login is 401, and lack of permission is 403. Returning 200 with an error hidden in the body confuses tools and developers.
Add a consistent error body with a machine-readable code, a human-readable message and, for validation failures, which field was wrong. A client developer should be able to fix a problem without messaging you. Never expose internal details such as stack traces or database messages to the outside.
How do you handle lists, filtering and large data?
Never return an unlimited list. Add paging with a limit and either page numbers or a cursor, and document the maximum page size. Support filtering and sorting through query parameters, such as status and created date, so clients do not download everything and filter themselves.
For very large or changing datasets, cursor-based paging is more reliable than page numbers, since new records do not shift the pages. Where clients need to know about changes, consider webhooks or an updated-since filter instead of forcing them to poll constantly.
Why do versioning and idempotency matter?
Your API will change, but integrations built by others cannot change on your timetable. Put a version in the address or header, keep old versions working for an announced period and avoid removing fields without notice. Adding optional fields is generally safe; renaming or removing them is not.
Networks fail, and clients retry. If a client resends a request to create a payment or an order after a timeout, you must not create two. Accept an idempotency key on create operations so repeated requests give the same result. This single habit prevents many costly duplicate records in finance and e-commerce integrations.
- Version from day one and announce deprecations early
- Accept an idempotency key on create operations
- Keep response shapes stable between minor changes
- Document rate limits and how clients should retry
What documentation and tooling help most?
Publish an API description using a standard format such as OpenAPI, and generate interactive documentation from it. Include real example requests and responses, authentication steps and a list of error codes. Provide a sandbox so partners can test without touching live data.
Add automated tests for the contract so changes that break clients are caught before release. A Plus Solution designs and builds APIs and integrations between business tools, and in such projects well-documented, predictable interfaces consistently reduce the time partners need to go live.
Frequently asked questions
Is REST the only way to build an API?
No. GraphQL, gRPC and webhooks suit different needs. REST remains widely used and well understood, which makes it a safe default for business integrations.
Should we use PUT or PATCH for updates?
PUT usually replaces the whole record, while PATCH changes only the fields sent. PATCH is often friendlier for clients; whichever you choose, document it.
How long should we support an old API version?
Long enough for integrators to migrate, which depends on your partners. Announce dates clearly and watch usage before switching a version off.
Do we need an API gateway?
Not for every project. A gateway helps when you manage many APIs, need central authentication, rate limiting and analytics.
Need help with this? Ask us a question about it — we reply within one working day.
