cognite-function-apps 0.11.0

FastAPI-style framework for building composable Function Apps for Cognite Functions with automatic OpenAPI schema generation and MCP integration

Function Apps

⚠️ IMPORTANT: This project has been renamed

Previously known as Cognite Typed Functions (cognite-typed-functions)

What changed:

• Package name: cognite-typed-functions → cognite-function-apps
• Import path: from cognite_typed_functions → from cognite_function_apps
• CLI command: ctf → fun

For existing users: Update your dependencies and change all imports. All class names and APIs remain unchanged.

Enterprise-grade framework for building composable Function Apps for Cognite Functions with automatic validation, built-in introspection, and AI integration.

Why Function Apps?

Standard Cognite Functions require a simple handle(client, data) function, which becomes unwieldy for complex APIs. This framework provides composable architecture, automatic validation, and built-in introspection.

Standard Cognite Function:

def handle(client, data):
    try:
        asset_no = int(data["assetNo"])  # Manual validation
        include_tax = data.get("includeTax", "false").lower() == "true"  # Manual parsing
        # Handle routing manually based on data
        if data.get("action") == "get_item":
            # Implementation here
        elif data.get("action") == "create_item":
            # Different implementation
    except Exception as e:
        return {"error": str(e)}  # Basic error handling

With Function Apps:

@app.get("/items/{item_id}")
def get_item(client: CogniteClient, item_id: int, include_tax: bool = False) -> ItemResponse:
    """Retrieve an item by ID"""
    # Type validation and coercion handled automatically
    # Clear function signature with proper types
    # Automatic error handling and response formatting

Key Features

• Type-safe routing - Decorator-based syntax with automatic validation
• Async/await support - Write both sync and async handlers
• Error handling - Comprehensive error handling with structured responses
• Logging - Enterprise logging with dependency injection
• Distributed tracing - OpenTelemetry-based tracing
• Dependency injection - Inject custom dependencies
• Introspection - Built-in schema, routes, health endpoints
• Model Context Protocol - Native AI tool exposure
• Local development server - Test locally with interactive API docs
• Function client - Notebook-first client for exploring functions

Installation

Requirements:

• Python 3.10 or higher
• uv (recommended) or pip

# Install the package
pip install cognite-function-apps

# Optional: Install with CLI support for dev server
pip install cognite-function-apps[cli]

# Optional: Install with tracing support
pip install cognite-function-apps[tracing]

Quick Start

from cognite.client import CogniteClient
from pydantic import BaseModel
from cognite_function_apps import FunctionApp, create_function_service

# Create your app
app = FunctionApp(title="My API", version="1.0.0")

# Define your models
class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None

class ItemResponse(BaseModel):
    id: int
    item: Item
    total_price: float

# Define your endpoints
@app.get("/items/{item_id}")
def get_item(
    client: CogniteClient,
    item_id: int,
    include_tax: bool = False
) -> ItemResponse:
    """Retrieve an item by ID"""
    item = Item(
        name=f"Item {item_id}",
        price=100.0,
        tax=10.0 if include_tax else None
    )
    total = item.price + (item.tax or 0)
    return ItemResponse(id=item_id, item=item, total_price=total)

@app.post("/items/")
def create_item(client: CogniteClient, item: Item) -> ItemResponse:
    """Create a new item"""
    new_id = 12345  # Your creation logic here
    total = item.price + (item.tax or 0)
    return ItemResponse(id=new_id, item=item, total_price=total)

# Export the handler for Cognite Functions
handle = create_function_service(app)

Test Locally

Install with CLI support and run the development server:

pip install cognite-function-apps[cli]
fun serve examples/

Visit http://localhost:8000/docs for interactive API documentation.

See the Local Development Server guide for detailed setup instructions.

Examples

The framework includes a complete example in examples/handler.py demonstrating:

• Type-safe routing with decorator syntax
• MCP integration for AI tool exposure
• Built-in introspection endpoints
• Async handler support
• Composable app architecture

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Acknowledgments

• Built specifically for Cognite Data Fusion Functions platform
• Decorator routing syntax inspired by FastAPI
• Data validation powered by Pydantic