Building Custom MCP Servers

// my-company-mcp/index.js
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";

const server = new Server({
  name: "my-company-tools",
  version: "1.0.0"
}, {
  capabilities: { tools: {}, resources: {}, prompts: {} }
});

// Register a tool
server.setRequestHandler("tools/call", async ({ params }) => {
  if (params.name === "get_jira_issue") {
    const issue = await jiraClient.getIssue(params.arguments.issue_key);
    return {
      content: [{ type: "text", text: JSON.stringify(issue) }]
    };
  }
});

// Register tool definitions
server.setRequestHandler("tools/list", async () => ({
  tools: [{
    name: "get_jira_issue",
    description: "Fetch a Jira issue by key. Returns title, description, status, and comments.",
    inputSchema: {
      type: "object",
      properties: {
        issue_key: { type: "string", description: "Jira issue key, e.g. PROJ-123" }
      },
      required: ["issue_key"]
    }
  }]
}));

const transport = new StdioServerTransport();
await server.connect(transport);

my-company-plugin/
  plugin.json           # Plugin manifest
  servers/
    jira/
      index.js          # MCP server entry point
      package.json
  skills/
    create-issue.md     # Claude skill that uses the MCP tools
  README.md

// plugin.json
{
  "name": "my-company-tools",
  "version": "1.0.0",
  "description": "Internal tools for Acme Corp development workflow",
  "mcpServers": {
    "jira": {
      "command": "node",
      "args": ["servers/jira/index.js"],
      "env": {
        "JIRA_API_TOKEN": "${JIRA_API_TOKEN}",
        "JIRA_DOMAIN": "${JIRA_DOMAIN}"
      }
    }
  }
}

// Expose resources (data Claude can @-reference)
server.setRequestHandler("resources/list", async () => ({
  resources: [{
    uri: "jira://recent-issues",
    name: "Recent Jira Issues",
    description: "Issues created or updated in the last 7 days"
  }]
}));

// Expose prompts (slash commands)
server.setRequestHandler("prompts/list", async () => ({
  prompts: [{
    name: "create-issue-from-bug",
    description: "Create a Jira issue from a bug report",
    arguments: [
      { name: "description", description: "Bug description", required: true }
    ]
  }]
}));