AJM Softwares · Technical note
Describe the work in terms of resources and actions
Start with the tasks a client needs to complete and the information it needs to read or change. Give resources stable identifiers, make relationships explicit, and define how collections are filtered and paginated. Avoid making clients infer business rules from endpoint names or undocumented response fields.
Write down each operation's authentication needs, required inputs, possible outputs, side effects, and failure cases. An OpenAPI description can make this interface readable by people and usable by documentation, client generation, and testing tools.
Use HTTP semantics consistently
Choose request methods and response status codes according to what the operation did. Clients and intermediaries use these semantics to decide whether a request succeeded, whether more action is needed, and how an error should be handled. Do not return a success code with an error-shaped body and expect every client to notice.
Think through retries when an operation changes state. A network timeout can leave the client uncertain whether the server completed the work. Define whether a request can be repeated safely and what identifier or lookup lets the client resolve an uncertain result.
Make validation errors useful and predictable
Validate incoming data at the server boundary and return a stable error shape that helps a client correct the request. RFC 9457 defines a standard format for machine-readable HTTP problem details; teams can add documented fields for domain-specific validation feedback where needed.
Keep client-facing error details separate from debugging information. Do not send stack traces, SQL errors, tokens, or other internal details in a response. Log enough server-side context to investigate the failure without making implementation internals part of the public contract.
Plan for clients that upgrade at different times
Treat a published API as a contract with clients you may not control. Review changes to field names, required values, meanings, and error behavior for compatibility. Document additions and deprecations, give consumers a transition path, and remove old behavior only after the agreed migration period.
Keep the OpenAPI description and implementation in sync. Validate example requests and responses in automated checks, and test important client workflows against the contract before release. A document that describes an API accurately is more valuable than a large specification that has drifted from production.