Azure Functions Development Skill

Overview

This skill helps you build Azure Functions using the Python v2 programming model with decorators.

Key Patterns

HTTP Trigger Function

import azure.functions as func
import json

app = func.FunctionApp(http_auth_level=func.AuthLevel.FUNCTION)

@app.function_name(name="my_function")
@app.route(route="api/endpoint", methods=["GET", "POST"])
def my_function(req: func.HttpRequest) -> func.HttpResponse:
    """HTTP trigger function with proper error handling."""
    try:
        # Parse request
        data = req.get_json() if req.method == "POST" else dict(req.params)
        
        # Your logic here
        result = {"status": "success", "data": data}
        
        return func.HttpResponse(
            body=json.dumps(result),
            status_code=200,
            mimetype="application/json"
        )
    except Exception as e:
        return func.HttpResponse(
            body=json.dumps({"error": str(e)}),
            status_code=500,
            mimetype="application/json"
        )

MCP Tool Trigger

@app.generic_trigger(
    arg_name="context",
    type="mcpToolTrigger",
    toolName="my_tool",
    description="What this tool does and when to use it",
    toolProperties='[{"propertyName": "input", "propertyType": "string", "description": "The input parameter"}]'
)
def my_tool(context) -> str:
    """MCP tool function."""
    content = json.loads(context)
    input_value = content["arguments"].get("input", "")
    return json.dumps({"result": input_value})

Configuration Files

host.json (Runtime Config)

{
  "version": "2.0",
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[4.*, 5.0.0)"
  },
  "extensions": {
    "mcp": {
      "enabled": true
    }
  }
}

local.settings.json (Local Development)

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "python",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "AzureWebJobsFeatureFlags": "EnableWorkerIndexing"
  }
}

Local Development Commands

# Start Azurite storage emulator (required)
azurite --silent --location /tmp/azurite

# Start the function app locally
cd src/function_app_directory
func start

# Install Azure Functions Core Tools (macOS)
brew tap azure/functions
brew install azure-functions-core-tools@4

Deployment with Azure Developer CLI

# Initialize project from template
azd init --template <template-name> -e <environment-name>

# Deploy to Azure
azd up

# Get function keys
az functionapp keys list --resource-group <rg> --name <app-name>

Common Issues and Solutions

Best Practices

1. Always use type hints for better IDE support
2. Log important operations with logging.info() and logging.error()
3. Return JSON responses with appropriate status codes
4. Use FUNCTION auth level for production (not ANONYMOUS)
5. Test locally with func start before deploying