Tool Registration

Each entry in tools becomes an MCP tool:

{
  name: 'mm_harvest_list_projects',
  description: 'List active Harvest projects with budget and client.',
  inputSchema: z.object({ project_path: z.string() }),
  handler: async (args) => ({ content: [{ type: 'text', text: '…' }] })
}

Names

mm_-prefixed, unique across every loaded plugin and built-in. A collision refuses the whole plugin, so nothing silently shadows a core tool.

Schemas

Zod in, JSON Schema out. Describe each field — agents choose arguments from those descriptions alone. Optional fields need sensible defaults; an agent won’t guess.

Visibility

Bundled plugin tools belong to a tool group (harvest, slack, trello, voice, imports) and are hidden until that group is opted into with MM_TOOL_GROUPS. A community plugin’s tools belong to no group, so they’re always listed.

Hidden never means disabled — any tool still runs when called by name.

Errors

Throw with a message a person can act on (“no Harvest token — set HARVEST_ACCESS_TOKEN”). The agent shows it to the user.