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Problem Details (problem+json)

When a request fails validation, BurgerAPI returns a 422 with a structured error body in the Problem Details format (application/problem+json), which follows the shape described in RFC 9457.

Set it explicitly​

Problem Details is the default. If you want to be explicit, set errorFormat: "problem+json" in the Burger constructor:

src/index.ts
import { Burger } from "burger-api";

const app = new Burger({
  apiDir: "./src/api",
  validation: { errorFormat: "problem+json" },
});

The response shape​

This is the actual response for GET /api/items?limit=abc against a query: z.object({ limit: z.number() }) schema:

{
  "type": "about:blank",
  "title": "Validation Error",
  "status": 422,
  "detail": "query: Invalid input: expected number, received string",
  "errors": {
    "query": [
      {
        "path": ["limit"],
        "message": "Invalid input: expected number, received string",
        "code": "invalid_type"
      }
    ]
  }
}

title is always "Validation Error" for request validation failures; for other framework errors it is the HTTP status phrase ("Not Found", "Unsupported Media Type", "Internal Server Error", and so on). errors groups issues by the validation slot that failed (query, params, headers, cookies, or body). Each entry carries the path (where the problem is), a message (what went wrong), and (for Zod) a code. The Content-Type is application/problem+json.

Safe in production​

Whether you use the default format or the plain alternative, production error bodies never include stack traces, source paths, or schema internals. Only the path, message, and code of each issue are returned. Development responses add diagnostics such as stack and cause, and 500 details are replaced with "Internal Server Error" in production.

Custom errors​

If you need a different shape entirely, provide your own errorRenderer in configuration. It receives the validation result and returns the Response you want.