new-tool

Adding a New MCP Tool

Steps

1. Create the handler file

Create <module>/<action>.js (example: email/archive.js) and keep the handler focused on business logic plus Graph calls:

const { getGraphClient } = require('../utils/graph-client');
const { formatResponse } = require('../utils/response-formatter');
const { makeResponse } = require('../utils/response-helpers');

async function handleArchiveEmail(args) {
  const client = await getGraphClient();
  // ... Graph API call ...
  const text = formatResponse(structuredData, textFallback);
  return makeResponse(text);
}

module.exports = handleArchiveEmail;

Follow core conventions from general.mdc for error handling and shared response patterns.

2. Register in module index

Edit <module>/index.js:

const handleArchiveEmail = require('./archive');

const emailTools = [
  // ... existing tools ...
  {
    name: "archive-email",
    description: "Moves an email to the archive folder",
    inputSchema: {
      type: "object",
      properties: {
        id: { type: "string", description: "Email ID to archive" }
      },
      required: ["id"]
    },
    handler: handleArchiveEmail
  }
];

Use the module's {module}Tools array (emailTools, calendarTools, etc.). The root index.js aggregates these arrays into TOOLS.

3. Add config fields if needed

If the tool needs new Graph API field selections or constants, add them to config.js.

4. Write tests

Create test/<module>/<action>.test.js following the patterns in the testing rule.

5. Update CLAUDE.md

Update docs when the tool adds new capabilities or config requirements.

Checklist

• Handler file exports one async handler function
• Handler uses getGraphClient() and Graph SDK fluent calls
• Tool registered in <module>/index.js under {module}Tools with name, description, inputSchema, handler
• New constants/field sets are added in config.js when required
• Test file created in test/<module>/ (follow testing.mdc)
• Core conventions in general.mdc are followed