> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fortressproductivity.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Reference

> Implementation and operation notes for Fortress.

Use this section when you are connecting agent runtimes, calling the REST API directly, or running Fortress locally.

<Columns cols={2}>
  <Card title="MCP reference" icon="terminal" href="/developers/mcp">
    Agent transport, resources, tools, prompts, subscriptions, and auth.
  </Card>

  <Card title="REST reference" icon="braces" href="/developers/rest">
    Base URL, auth modes, list envelopes, and primary endpoints.
  </Card>

  <Card title="Local development" icon="laptop" href="/developers/local-development">
    Run the monorepo, database, migrations, seeds, tests, and checks.
  </Card>

  <Card title="Billing and limits" icon="badge-dollar-sign" href="/operate/billing-limits">
    Free-plan caps, Pro behavior, and history visibility.
  </Card>
</Columns>

## Architecture at a glance

| Package            | Purpose                                                                               |
| ------------------ | ------------------------------------------------------------------------------------- |
| `packages/shared`  | Zod schemas, TypeScript types, enums, queue helpers, and shared API shapes.           |
| `packages/api`     | Hono REST API, MCP server, Drizzle ORM, migrations, services, billing, and telemetry. |
| `packages/web`     | React SPA with TanStack Router and TanStack Query.                                    |
| `packages/desktop` | Electron macOS wrapper around the live web app.                                       |

## Key idea for integrations

Fortress has two external surfaces:

* **REST** for web, mobile, desktop, and direct service integrations.
* **MCP** for agents, with resources for reads and tools for actions.

Most agent clients should prefer MCP. Direct REST calls are useful for internal apps, automation, admin scripts, and debugging.