Azure Functions OpenAPI with Pydantic

A lightweight, modern OpenAPI decorator for Azure Functions with full Pydantic support. Generate accurate API documentation with minimal code.

Features

• 🎯 Simple decorator syntax - Just add @openapi() to your functions
• 📝 Pydantic integration - Define request/response models with validation
• 🔄 Response envelope - Standardized {success, data, error} format
• 🏗️ Nested models - Automatically expands nested Pydantic models in docs
• ⚡ Blueprint support - Works seamlessly with Azure Functions blueprints
• 📊 Smart defaults - Auto-generates HTTP status codes based on your endpoint

Installation

pip install azure-functions-openapi-pydantic

Quick Start

from azure.functions import HttpRequest, HttpResponse, Blueprint
from pydantic import BaseModel, Field, EmailStr
from azfunc_openapi_pydantic import openapi, ApiResponse, OpenAPIBlueprint

# Define your models
class CreateUserRequest(BaseModel):
    name: str = Field(..., min_length=1, max_length=100)
    email: EmailStr

class User(BaseModel):
    id: str
    name: str
    email: EmailStr
    created_at: str

# Create blueprint with OpenAPI support
api_bp = OpenAPIBlueprint()

# Decorate your function
@api_bp.route(route="users", methods=["POST"])
@openapi(request=CreateUserRequest, response=User)
def create_user(req: HttpRequest) -> HttpResponse:
    """Create a new user"""
    body = req.validated_body  # Validated Pydantic model attached by decorator
    
    user = User(
        id="usr_123",
        name=body.name,
        email=body.email,
        created_at="2025-01-01T00:00:00Z"
    )
    
    return ApiResponse.ok(user, status_code=201)

Generate OpenAPI Spec & Docs

from azfunc_openapi_pydantic import generate_openapi_spec, generate_swagger_ui
import json

@app.route(route="openapi.json", methods=["GET"])
def openapi_spec(req: HttpRequest) -> HttpResponse:
    spec = generate_openapi_spec(title="My API", version="1.0.0")
    return HttpResponse(json.dumps(spec, indent=2), mimetype="application/json")

@app.route(route="docs", methods=["GET"])
def swagger_ui(req: HttpRequest) -> HttpResponse:
    return generate_swagger_ui(title="My API Documentation")

Response Envelope

All responses follow a consistent envelope format:

Success:

{
  "success": true,
  "data": { /* your response model */ },
  "error": null
}

Error:

{
  "success": false,
  "data": null,
  "error": "Error message"
}

Decorator Options

@openapi(
    request=RequestModel,      # Pydantic model for POST/PUT body
    response=ResponseModel,    # Pydantic model for response data
    params={"id": str},        # Query/path parameters
    tags=["Users"],            # OpenAPI tags
    summary="Custom summary",  # Override function docstring
    errors={404: "Not found"}  # Custom error responses
)

Nested Models

Nested Pydantic models are automatically expanded in the OpenAPI spec:

class Address(BaseModel):
    street: str
    city: str
    country: str = "US"

class UserProfile(BaseModel):
    user: User
    address: Address
    preferences: dict

@openapi(response=UserProfile)
def get_profile() -> HttpResponse:
    # OpenAPI spec will show full nested structure
    ...

Examples

Check out the examples/ directory for a complete working Azure Functions app demonstrating:

• Full CRUD operations
• Request validation and error handling
• Nested models and complex data structures
• Pagination and query parameters
• OpenAPI spec generation
• Swagger UI integration

To run the example:

cd examples
pip install -r requirements.txt
func start

Then visit http://localhost:7071/api/docs for interactive API documentation.

License

MIT