SCHEMA001errorFree tier

pydantic-nullability-mismatch

Pydantic response model requires field that is nullable in database or missing in data sources.

Applies to: Project-level

Why this matters

When a Pydantic response model marks a field as required (non-Optional) but the database column is nullable, or raw SQL/test fixtures don't populate it, you'll get 500 Internal Server Errors at runtime. FastAPI's ResponseValidationError surfaces during serialization, making these bugs hard to trace back to their origin. Ensure all required response fields are always populated.

Catch it before it ships

pip install stablestack # or: npx stablestackstablestack # scans your project, SCHEMA001 includedstablestack explain SCHEMA001

False positive in your codebase? Suppress a single line with # noqa: SCHEMA001

More Schema Validation checks

SCHEMA002

pydantic-sqlalchemy-field-mismatch

Pydantic ORM schema references field that doesn't exist in SQLAlchemy model.