[Feature request] Scaffold MCP server project with func init

[lilyjma]

Problem Statement

Developers who want to deploy a self-hosted MCP server currently need to manually add Function artifacts to their project. This involves creating and populating host.json and local.settings.json with the appropriate defaults. Manual setup is error-prone and slows down onboarding. We propose to introduce a new flag, --configurationProfile, to the func init command, streamlining this process.

User Experience

Minimal Example

In an existing MCP server project, a developer runs:

func init --configurationProfile mcp-custom-handler --worker-runtime <python|node|dotnet>

The command scaffolds the project with the following files and settings:

host.json

{
    "version": "2.0",
    "configurationProfile": "mcp-custom-handler",
    "customHandler": {
        "description": {
            "defaultExecutablePath": "",
            "arguments": []
        }
    }
}

local.settings.json

{
    "IsEncrypted": false,
    "Values": {
        "FUNCTIONS_WORKER_RUNTIME": "<python|node|dotnet-isolated>",
        "AzureWebJobsFeatureFlags": "EnableMcpCustomHandlerPreview"
    }
}

• The language value is set based on the --worker-runtime flag.
• The feature flag for MCP custom handler is set.

Requirements

• New flag: Add --configurationProfile to the func init command.
• Supported value: Only mcp-custom-handler is supported for now. Other values are invalid and should be rejected with a clear error.
• Validation: If an unsupported configurationProfile value is provided, the CLI should fail with an error message:
  "configurationProfile '<value>' is not supported. Supported values: mcp-custom-handler."
• File Output:
  • Generate a host.json file with the profile and relevant defaults.
  • Generate a local.settings.json file with the proper worker runtime and feature flag.
• Override Precedence: If the files already exist, do not overwrite them; warn the user or prompt for overwrite.
• Extensibility: Future profiles may be added; for now, extensibility is out-of-scope.

func pack requirements

• Remove need for requirements.txt and .azurefunctions directory when the FWR is python and dotnet-isolated, respectively.

  Changes have been made to remove the need for requirements.txt and .azurefunctions directory. However, func pack is still checking for the presence of these artifacts and blocking the zip.

  • .NET isolated issue: func pack errors in custom handler project because 'functions.metadata' not found #4677
  • Python:
    

Acceptance Criteria

• Running func init --configurationProfile mcp-custom-handler --worker-runtime <python|node|dotnet> in a project creates a host.json and local.settings.json as specified, with the correct values substituted.
• The CLI fails with a clear error for unsupported --configurationProfile values.
• Running the command in a directory with existing config files does not overwrite them without user consent.

Testing plan

• Regression: Ensure other func init scenarios remain unchanged.

Work Items

[ ] Add --configurationProfile flag to func init.
[ ] Implement supported value: mcp-custom-handler.
[ ] Generate host.json and local.settings.json with correct values.
[ ] Handle existing files gracefully.
[ ] Add tests for new functionality.
[ ] Update documentation.

[lilyjma]

Tested with the Core Tools v4.4.0. Project created with the --configurationProfile mcp-custom-handler flag doesn't include the content specified above.

[liliankasem]

Tested with the Core Tools v4.4.0. Project created with the --configurationProfile mcp-custom-handler flag doesn't include the content specified above.

Can you expand on what content is missing?

Here's the output of this command:

You are using a preview feature. Configuration profiles may change in future releases.

▸ Applying configuration profile: mcp-custom-handler
[host.json] ✓ Set configuration profile to 'mcp-custom-handler'
[host.json] ✓ Configured custom handler settings for MCP
[host.json] Creating new at /Users/likasem/Desktop/mcptest/host.json
[local.settings.json] ✓ Added feature flag 'EnableMcpCustomHandlerPreview'
[local.settings.json] Creating new at /Users/likasem/Desktop/mcptest/local.settings.json

And if the files already exist

'local.settings.json' found in root directory (/Users/likasem/Desktop/mcptest).
Resolving worker runtime to 'dotnet-isolated'.

You are using a preview feature. Configuration profiles may change in future releases.

▸ Applying configuration profile: mcp-custom-handler
[host.json] ⚠ Already configured (use --force to overwrite)
[local.settings.json] ⚠ Already configured (use --force to overwrite)

If the profile doesn't exist

'local.settings.json' found in root directory (/Users/likasem/Desktop/mcptest).
Resolving worker runtime to 'dotnet-isolated'.

Configuration profile 'mcp-custom-hand' is not supported. Supported values: mcp-custom-handler

local.settings.json

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "AzureWebJobsFeatureFlags": "EnableMcpCustomHandlerPreview"
  }
}

host.json

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "excludedTypes": "Request"
      }
    }
  },
  "configurationProfile": "mcp-custom-handler",
  "customHandler": {
    "description": {
      "defaultExecutablePath": "",
      "workingDirectory": "",
      "arguments": []
    }
  }
}

The func pack requirements were not part of the initial issue when this work item was being worked on - I would suggest opening a new issue for this.

[lilyjma]

@liliankasem - apologies for the delay. I'm still seeing what I saw before with the latest version of Core Tools, i.e. 4.5.0 today. I ran the init command inside an empty directory -

lily@MacBook-Pro-2 1202python-test % func --version
4.5.0

lily@MacBook-Pro-2 1202python-test % func init --configurationProfile mcp-custom-handler --worker-runtime python

Found Python version 3.10.11 (python3).
The new Python programming model is generally available. Learn more at https://aka.ms/pythonprogrammingmodel
Writing requirements.txt
Writing function_app.py
Writing .gitignore
Writing host.json
Writing local.settings.json
Writing /Users/lily/Desktop/Functions/mcp/tests/coretools-test/1202python-test/.vscode/extensions.json
lily@MacBook-Pro-2 1202python-test % cat function_app.py 
import azure.functions as func
import datetime
import json
import logging

app = func.FunctionApp()%                                                                                                                                                                                    lily@MacBook-Pro-2 1202python-test % cat host.json 
{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "excludedTypes": "Request"
      }
    }
  },
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[4.*, 5.0.0)"
  }
}%                                                                                                                                                                                                           lily@MacBook-Pro-2 1202python-test % cat local.settings.json 
{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "python",
    "AzureWebJobsStorage": "UseDevelopmentStorage=true"
  }
}%                                                                                                                                                                                                          

With .NET, it's similar -

lily@MacBook-Pro-2 1202python-test % cat host.json 
{
    "version": "2.0",
    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    }
}%                                                                                                                                                                                                           lily@MacBook-Pro-2 1202python-test % cat local.settings.json 
{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_INPROC_NET8_ENABLED": "1",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet"
    }
}%