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

# Reference overview

> The wiring layer — CLI, MCP server, and REST API for custom integrations.

# Reference overview

> **Coming soon.** This page lands in the next content pass.

Product Brain exposes the **Chain** (the kernel) through **wiring**: the `pb` CLI, the MCP server, and HTTP endpoints. This tab is for **host environments** (Cursor, Claude, ChatGPT, Codex, terminal) where you install that wiring and for **Staff+ engineers** who script against the same contracts.

**What you'll find here:**

* Install paths and auth for CLI, MCP, and REST
* Session lifecycle and orient commands
* Error envelopes and troubleshooting

**In the meantime:**

* Start with [CLI overview](/docs/cli/overview) or [MCP overview](/docs/mcp/overview)
* See [The Chain](/docs/the-chain) for what the kernel stores (no Convex required to understand the model)