Pydantic Models

---
name: pydantic-models-py
description: "Create Pydantic models following the multi-model pattern for clean API contracts."
risk: critical
source: community
date_added: "2026-02-27"
---

# Pydantic Models

Create Pydantic models following the multi-model pattern for clean API contracts.

## Quick Start

Use the inline model patterns below and adapt class names and fields to the actual API contract. Inspect the installed Pydantic version before selecting configuration syntax; these fragments require the imports and application types shown by your project. Do not assume a standalone template file is bundled.

## Multi-Model Pattern

| Model | Purpose |
|-------|---------|
| `Base` | Common fields shared across models |
| `Create` | Request body for creation (required fields) |
| `Update` | Request body for updates (all optional) |
| `Response` | API response with all fields |
| `InDB` | Database document with `doc_type` |

## camelCase Aliases

```python
class MyModel(BaseModel):
    workspace_id: str = Field(..., alias="workspaceId")
    created_at: datetime = Field(..., alias="createdAt")
    
    class Config:
        populate_by_name = True  # Accept both snake_case and camelCase
```

## Optional Update Fields

```python
class MyUpdate(BaseModel):
    """All fields optional for PATCH requests."""
    name: Optional[str] = Field(None, min_length=1)
    description: Optional[str] = None
```

## Database Document

```python
class MyInDB(MyResponse):
    """Adds doc_type for Cosmos DB queries."""
    doc_type: str = "my_resource"
```

## Integration Steps

1. Create models in `src/backend/app/models/`
2. Export from `src/backend/app/models/__init__.py`
3. Add corresponding TypeScript types

## When to Use
This skill is applicable to execute the workflow or actions described in the overview.

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.