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.