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FunctionsMcpTool Sample

A sample MCP server built with Azure Functions (Java) that demonstrates saving and retrieving code snippets using Azure Blob Storage.

What It Does

This sample exposes three MCP tools:

Tool Description
HelloWorld Says hello and logs the messages you provide.
SaveSnippets Saves a text snippet to Azure Blob Storage.
GetSnippets Retrieves a previously saved snippet by name.

Prerequisites

Getting Started

1. Start the Storage Emulator

The snippet tools persist data in Azure Blob Storage. For local development, start Azurite:

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

Or use the Azurite VS Code extension and run Azurite: Start.

2. Build and Run

cd samples/FunctionsMcpTool
mvn clean package
mvn azure-functions:run

The MCP endpoint will be available at http://localhost:7071/runtime/webhooks/mcp.

3. Connect from VS Code

Open .vscode/mcp.json at the repo root. Find the server called local-mcp-function and click Start above the name.

4. Try the Tools

In Copilot chat (agent mode), try prompts like:

Say Hello
Save this snippet as snippet1
Retrieve snippet1 and apply to MyFile.java

Source Code

File Description
HelloWorld.java Simple tool that logs messages and says hello.
Snippets.java Save and retrieve snippets using @BlobOutput / @BlobInput bindings.
McpToolInvocationContext.java POJO for the MCP tool invocation context.

Key Concepts

MCP Tool Trigger — The @McpToolTrigger annotation exposes a Java function as an MCP tool:

@FunctionName("SaveSnippets")
@StorageAccount("AzureWebJobsStorage")
public String saveSnippet(
        @McpToolTrigger(
                name = "saveSnippets",
                description = "Saves a text snippet to your snippets collection.")
        String mcpToolInvocationContext,
        @McpToolProperty(name = "snippetName", propertyType = "string",
                description = "The name of the snippet.", isRequired = true)
        String snippetName,
        @McpToolProperty(name = "snippet", propertyType = "string",
                description = "The content of the snippet.", isRequired = true)
        String snippet,
        @BlobOutput(name = "outputBlob", path = BLOB_PATH)
        OutputBinding<String> outputBlob,
        final ExecutionContext functionExecutionContext) {
    outputBlob.setValue(snippet);
    return "Successfully saved snippet '" + snippetName + "'";
}

MCP Tool Properties — Use @McpToolProperty to declare input parameters that the MCP client passes to your tool.

Azure Bindings — Standard Azure Functions bindings (@BlobInput, @BlobOutput, @StorageAccount) work seamlessly with MCP triggers.