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Getting Started with Remote MCP Servers using Azure Functions (.NET/C#)

This is a quickstart template to easily build and deploy a custom remote MCP server to the cloud using Azure functions. You can clone/restore/run on your local machine with debugging, and azd up to have it in the cloud in a couple minutes. The MCP server is secured by design using keys and HTTPs, and allows more options for OAuth using EasyAuth and/or API Management as well as network isolation using VNET.

If you're looking for this sample in more languages check out the Node.js/TypeScript and Python samples.

Prerequisites

• .NET 8 SDK
• Azure Functions Core Tools
• Azure Developer CLI
• To use Visual Studio to run and debug locally:
  • Visual Studio 2022.
  • Make sure to select the Azure development workload during installation.
• To use Visual Studio Code to run and debug locally:
  • Visual Studio Code
  • Azure Functions extension

Below is the architecture diagram for the Remote MCP Server using Azure Functions:

Prepare your local environment

An Azure Storage Emulator is needed for this particular sample because we will save and get snippets from blob storage.

1. Start Azurite

   docker run -p 10000:10000 -p 10001:10001 -p 10002:10002 \
       mcr.microsoft.com/azure-storage/azurite
   

Note if you use Azurite coming from VS Code extension you need to run Azurite: Start now or you will see errors.

Run your MCP Server locally from the terminal

1. From the src folder, run this command to start the Functions host locally:

   cd src
   func start
   

Note by default this will use the webhooks route: /runtime/webhooks/mcp/sse. Later we will use this in Azure to set the key on client/host calls: /runtime/webhooks/mcp/sse?code=<system_key>

Use the MCP server from within a client/host

VS Code - Copilot Edits

1. Add MCP Server from command palette and add URL to your running Function app's SSE endpoint:

   http://0.0.0.0:7071/runtime/webhooks/mcp/sse
   

2. List MCP Servers from command palette and start the server

3. In Copilot chat agent mode enter a prompt to trigger the tool, e.g., select some code and enter this prompt

   Say Hello 
   

   Save this snippet as snippet1 
   

   Retrieve snippet1 and apply to NewFile.cs
   

4. When prompted to run the tool, consent by clicking Continue

5. When you're done, press Ctrl+C in the terminal window to stop the func.exe host process.

MCP Inspector

1. In a new terminal window, install and run MCP Inspector

   npx @modelcontextprotocol/inspector node build/index.js
   

2. CTRL click to load the MCP Inspector web app from the URL displayed by the app (e.g. http://0.0.0.0:5173/#resources)

3. Set the transport type to SSE

4. Set the URL to your running Function app's SSE endpoint and Connect:

   http://0.0.0.0:7071/runtime/webhooks/mcp/sse
   

5. List Tools. Click on a tool and Run Tool.

Deploy to Azure for Remote MCP

Run this azd command to provision the function app, with any required Azure resources, and deploy your code:

azd up

You can opt-in to a VNet being used in the sample. To do so, do this before azd up

azd env set VNET_ENABLED true

Additionally, API Management can be used for improved security and policies over your MCP Server, and App Service built-in authentication can be used to set up your favorite OAuth provider including Entra.

Connect to your function app from a client

Your client will need a key in order to invoke the new hosted SSE endpoint, which will be of the form https://<funcappname>.azurewebsites.net/runtime/webhooks/mcp/sse. The hosted function requires a system key by default which can be obtained from the portal or the CLI (az functionapp keys list --resource-group <resource_group> --name <function_app_name>). Obtain the system key named mcp_extension.

For MCP Inspector, you can include the key in the URL: https://<funcappname>.azurewebsites.net/runtime/webhooks/mcp/sse?code=<your-mcp-extension-system-key>.

For GitHub Copilot within VS Code, you should instead set the key as the x-functions-key header in mcp.json, and you would just use https://<funcappname>.azurewebsites.net/runtime/webhooks/mcp/sse for the URL. The following example uses an input and will prompt you to provide the key when you start the server from VS Code:

{
    "inputs": [
        {
            "type": "promptString",
            "id": "functions-mcp-extension-system-key",
            "description": "Azure Functions MCP Extension System Key",
            "password": true
        }
    ],
    "servers": {
        "my-mcp-server": {
            "type": "sse",
            "url": "<funcappname>.azurewebsites.net/runtime/webhooks/mcp/sse",
            "headers": {
                "x-functions-key": "${input:functions-mcp-extension-system-key}"
            }
        }
    }
}

Redeploy your code

You can run the azd up command as many times as you need to both provision your Azure resources and deploy code updates to your function app.

[!NOTE] Deployed code files are always overwritten by the latest deployment package.

Clean up resources

When you're done working with your function app and related resources, you can use this command to delete the function app and its related resources from Azure and avoid incurring any further costs:

azd down

Source Code

The function code for the GetSnippet and SaveSnippet endpoints are defined in SnippetsTool.cs. The McpToolsTrigger attribute applied to the async Run method exposes the code function as an MCP Server.

This shows the code for a few MCP server examples (get string, get object, save object):

[Function(nameof(SayHello))]
public string SayHello(
    [McpToolTrigger(HelloToolName, HelloToolDescription)] ToolInvocationContext context
)
{
    logger.LogInformation("Saying hello");
    return "Hello I am MCP Tool!";
}

[Function(nameof(GetSnippet))]
public object GetSnippet(
    [McpToolTrigger(GetSnippetToolName, GetSnippetToolDescription)] ToolInvocationContext context,
    [BlobInput(BlobPath)] string snippetContent)
{
    return snippetContent;
}

[Function(nameof(SaveSnippet))]
[BlobOutput(BlobPath)]
public string SaveSnippet(
    [McpToolTrigger(SaveSnippetToolName, SaveSnippetToolDescription)] ToolInvocationContext context,
    [McpToolProperty(SnippetNamePropertyName, PropertyType, SnippetNamePropertyDescription)] string name,
    [McpToolProperty(SnippetPropertyName, PropertyType, SnippetPropertyDescription)] string snippet)
{
    return snippet;
}

Next Steps

• Add API Management to your MCP server
• Add EasyAuth to your MCP server
• Enable VNET using VNET_ENABLED=true flag
• Learn more about related MCP efforts from Microsoft