{
  "instruction": "Use Pydantic models with Field constraints and field_validator for all input",
  "relevant_when": "Agent creates or modifies a FastAPI application that accepts user input, adds POST/PUT/PATCH endpoints",
  "context": "FastAPI uses Pydantic for input validation, but agents often create models without field constraints. Every string must have min_length and max_length via Field(). Every integer must have range constraints (gt, ge, lt, le). Enum-like strings should use Field(pattern=). Complex validation uses @field_validator with @classmethod that raises ValueError.",
  "sources": [
    {
      "type": "file",
      "filename": "skills/fastapi-security-basics/SKILL.md",
      "tile": "tessl-labs/fastapi-security-basics@0.2.0"
    }
  ],
  "checklist": [
    {
      "name": "pydantic-models-defined",
      "rule": "Agent defines Pydantic BaseModel subclasses for all request bodies",
      "relevant_when": "Agent creates FastAPI endpoints that accept input"
    },
    {
      "name": "field-constraints-used",
      "rule": "Agent uses Field() with constraints (min_length, max_length, gt, ge, lt, le, pattern) on model fields",
      "relevant_when": "Agent creates Pydantic models for FastAPI"
    },
    {
      "name": "string-length-constraints",
      "rule": "Agent adds min_length and max_length constraints to string fields via Field()",
      "relevant_when": "Agent creates Pydantic models with string fields"
    },
    {
      "name": "integer-range-constraints",
      "rule": "Agent adds range constraints (gt, ge, lt, le) to integer fields via Field()",
      "relevant_when": "Agent creates Pydantic models with integer fields"
    },
    {
      "name": "field-validator-used",
      "rule": "Agent uses @field_validator decorator with @classmethod for complex validation logic that raises ValueError",
      "relevant_when": "Agent creates Pydantic models that need validation beyond simple Field constraints"
    },
    {
      "name": "endpoints-use-models",
      "rule": "Agent uses Pydantic models as type annotations on route handler parameters (not raw dict or untyped)",
      "relevant_when": "Agent creates FastAPI endpoints that accept input"
    }
  ]
}