First Attempt at MCP Server

2-minute read
AIMCP
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MCP History 🔗︎

MCP evolved from Function Call. Function Call is not a standardized protocol, and implementations vary widely. MCP unifies the protocol, decoupling tools from large models, and represents a further standardization of CodeAct. MCP is designed based on a client-server architecture, acting as an intermediary layer to bridge the gap between prompts and tool invocations.

MCP Features:

  • Automated decision-making via large models
  • Standardized interfaces
  • Tool modularization

A2A: Agent2Agent was proposed by Google. The Google Agent Development Kit (ADK) is a multi-agent suite.

MCP Server Implementation Notes 🔗︎

1. Basic Setup 🔗︎

const server = new McpServer({
    name: "ping-pong",
    version: "1.0.0",
    capabilities: {
        resources: {
            subscribe: true,
            listChanged: true
        }
    }
});

2. Resource Implementation 🔗︎

server.resource(
    "echo",                          // Resource name
    new ResourceTemplate(
        "echo://{message}",          // URI template
        {
            list: () => ({           // List callback
                resources: [{        // Must return an array of resources
                    uri: "echo://hello",
                    name: "Echo Resource",           // Required
                    description: "...",              // Required
                    mimeType: "text/plain"          // Required
                }]
            })
        }
    ),
    async (uri, { message }) => ({   // Read callback
        contents: [{
            uri: uri.href,
            mimeType: "text/plain",
            text: `Resource echo: ${message}`
        }]
    })
);

3. Common errors and solutions 🔗︎

  1. template.resourceTemplate.listCallback is not a function

    • Cause: ResourceTemplate parameter structure error
    • Solution: Ensure that the list callback function is passed correctly

  2. result.resources is not iterable

    • Cause: Incorrect format of list callback return
    • Solution: Ensure that the return format is { resources: [...] }

  3. Resource not found

    • Cause: URI mismatch
    • Solution: Ensure that the URI in the list matches the template format

  4. Required field missing

    • Cause: Required metadata fields are missing
    • Solution: Ensure that all required fields (name, description, mimeType) are included

4. Debugging Tools 🔗︎

  • MCP Inspector (v0.7.0) can be used for:
    • Viewing the list of available resources
    • Testing resource reading functionality
    • Verifying resource template configuration

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