# Schema Validation Failed (SCHEMA_VALIDATION_FAILED)

The incoming request body did not pass schema validation. The gateway validates
the request body against a JSON Schema defined in the route configuration and
rejects requests that do not conform.

## How schema validation works

When a route has a request body schema defined in the OpenAPI specification,
Zuplo automatically validates incoming request bodies against that schema. If
validation fails, the gateway returns a `400 Bad Request` response with details
about which fields failed validation.

## Common validation errors

- **Missing required fields** - The request body is missing one or more fields
  marked as `required` in the schema.
- **Wrong data type** - A field value does not match the expected type (for
  example, a string where a number is expected).
- **Invalid enum value** - A field value is not one of the allowed values
  defined in an `enum` constraint.
- **Pattern mismatch** - A string field does not match the regular expression
  defined in the `pattern` property.
- **Out of range** - A numeric value falls outside the `minimum` or `maximum`
  bounds defined in the schema.

## How to fix

1. Read the error response body carefully. It contains specific details about
   which fields failed validation and why.
2. Compare the request body against the JSON Schema defined in the route
   configuration.
3. Ensure all required fields are present and have the correct data types.
4. Validate the request body locally using a JSON Schema validator before
   sending the request.

:::tip

The validation error response includes the path to the invalid field and a
description of the constraint that failed. Use this information to quickly
identify and fix the issue.

:::

## How to configure schemas

Define request body schemas in the `routes.oas.json` file using standard JSON
Schema syntax within the OpenAPI `requestBody` definition. The schema specifies
required fields, data types, formats, and constraints for the request body.