API Request Validation Skill

Overview

This skill provides guidance and reusable components for implementing robust API request validation in Python, primarily using FastAPI and Pydantic.

It covers:

• Basic validation with Pydantic models.
• Custom validation logic for specific fields.
• Advanced validation scenarios like cross-field validation and query parameters.
• Standardized error handling for validation failures.

Getting Started

The most common validation tasks are broken down into reference files. Start with the one that best fits your needs.

• Basic Validation: If you're new to Pydantic or need to validate a simple data structure, see

  references/pydantic-models.md

  .
• Custom Rules: For validating specific formats like emails or password strength, see

  references/custom-validators.md

  .
• Complex Scenarios: For validating query parameters, file uploads, or dependencies between fields, see

  references/advanced-validation.md

  .
• Error Responses: To customize how validation errors are returned to the client, see

  references/error-handling.md

  .

Resources

references/

• pydantic-models.md

  : Guide to creating basic Pydantic models for request body validation.

• custom-validators.md

  : How to write custom validator functions for fields.

• advanced-validation.md

  : Covers cross-field validation, query parameters, and file uploads.

• error-handling.md

  : Instructions for creating a custom FastAPI exception handler for validation errors.

scripts/

• validators.py

  : A collection of reusable Pydantic validator functions (e.g., for email, password strength).

• error_handler.py

  : A pre-built FastAPI exception handler for

  RequestValidationError

  .

• main_example.py

  : A full FastAPI application demonstrating all validation techniques covered in this skill. You can run this file to see the validation in action.