Building a Module

Building a Module

Modules are source folders. One source can serve several service accounts; source changes affect all of them.

mcps/my-module/
├── manifest.json
├── index.js
└── instructions.md     optional client instructions

Copy _template or ask the Assistant to scaffold a source from sanitized API docs. The detailed module contract remains the implementation reference.

Minimal manifest

{
  "id": "weather",
  "slug": "weather_mcp",
  "name": "Weather",
  "icon": "⛅",
  "description": "Weather service tools",
  "version": "1.0.0",
  "settings": [
    { "key": "api_key", "label": "API key", "type": "secret", "required": true }
  ]
}

Supported form types are text, secret, select, and textarea. Use secret fields for credentials; ordinary source files are not encrypted secret storage. Keep IDs/slugs unique and non-reserved.

Registration shape

export function register({ server, z, getSettings }) {
  server.registerTool('check_configuration', {
    title: 'Check configuration',
    description: 'Check whether this account has an API key; does not test the service.',
    inputSchema: {}
  }, async () => {
    const configured = Boolean(getSettings().api_key);
    return {
      content: [{ type: 'text', text: configured ? 'API key supplied.' : 'Set an API key in Settings.' }],
      isError: !configured
    };
  });
}

Use a plain object of Zod fields for inputSchema, not z.object(). Platform helpers include fetchJson and global fetch; do not assume arbitrary npm dependencies are installed. Add an optional test(settings, {fetchJson}) export for a meaningful upstream connectivity check. The example above checks configuration only and never validates an upstream key.

Account-safe source

Get per-request settings from the injected getSettings() closure. Do not store credentials in module-global variables. Account snapshots prevent ordinary cross-request settings mutation, not malicious module access: JavaScript runs in the trusted station process.

Return actionable errors without secrets. Make destructive actions explicit and require appropriate confirmation. Review generated code, inspect Tools, test, and reload before enabling access. The Station management module is another privileged way to create/edit source remotely.

Share source, not state

Module ZIP export excludes managed configuration/chat, not arbitrary embedded secrets. Review it before sharing. Account records and usage require a full private backup. Backups.