# API errors: a contract for clients and operations

https://thiago.limaesilvatecnologia.com.br/en/artigos/error-contracts/

Published: 2026-09-12

Public responses and internal diagnostics serve different audiences.

Content produced with AI assistance for Thiago Silva’s website. Independent editorial analysis; it does not represent clients or employers.

Reading-path month: March 2026

Collection published on September 12, 2026. Months organize the reading path; they are not earlier publication dates.

A short architecture article. The technical reference supports the topic; hypothetical scenarios and assessment proposals are editorial analysis, not accounts of personal implementations.

## The architecture decision

An unexpected failure must be investigable without turning the user response into an infrastructure map. Error contracts belong in API design.

## Practical application

Editorial proposal: define client-friendly categories and an operational correlation identifier. In a hypothetical payment, distinguish business rejection from unavailability, avoiding retry advice that could duplicate a transaction.

## How to verify

Simulate dependency failures in testing and review responses, logs and consumer behavior. Confirm investigation is possible through the identifier without receiving secrets. A short message is useful only when matching diagnostics and a clear recovery path exist.

## Sources

- [OWASP — Error Handling Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Error_Handling_Cheat_Sheet.html). Accessed: 2026-09-12.

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