# Overview

Each guide on this page solves one task end-to-end. Pick the one that matches what you're trying to ship; come back for the rest as you grow.

<table data-view="cards"><thead><tr><th></th><th></th><th data-type="content-ref"></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td><strong>📊 Read a financial picture</strong></td><td>Pull balances, transactions, obligations, and counterparties for a tenant.</td><td><a href="/pages/srQkJDeBIoVx1YJ6sLg6">/pages/srQkJDeBIoVx1YJ6sLg6</a></td><td></td></tr><tr><td><strong>💸 Pay an invoice safely</strong></td><td>Propose a payment, route to approval if needed, execute, get a receipt.</td><td><a href="/pages/EvXLQlWSFcn9RYDpmBqe">/pages/EvXLQlWSFcn9RYDpmBqe</a></td><td></td></tr><tr><td><strong>🛡 Give an agent a spending limit</strong></td><td>Define a policy in plain English. Brain enforces it on every proposed action.</td><td><a href="/pages/Wnu4l8fn2PmQ5iXwBzAx">/pages/Wnu4l8fn2PmQ5iXwBzAx</a></td><td></td></tr><tr><td><strong>📜 Audit every action</strong></td><td>Pull a verifiable trail of what your agent (or user) did.</td><td><a href="/pages/Fypem4aaYkeJlDtrdFXd">/pages/Fypem4aaYkeJlDtrdFXd</a></td><td></td></tr><tr><td><strong>🔌 Let an external agent in</strong></td><td>Authorize an MCP-compatible agent to read and propose on a tenant's behalf.</td><td><a href="/pages/QlSPCaWGQFEIUdhwQS8v">/pages/QlSPCaWGQFEIUdhwQS8v</a></td><td></td></tr></tbody></table>

### What every guide assumes

| Assumption                    | How to satisfy                                            |
| ----------------------------- | --------------------------------------------------------- |
| You finished the Quickstart   | The SDK is installed, your API key works, a tenant exists |
| You're in sandbox             | Production works the same way; sandbox is just safer      |
| You're calling from a backend | Server keys never go in client-side code                  |

```typescript
import { Brain } from "@brain/sdk";

export const brain = new Brain({ apiKey: process.env.BRAIN_API_KEY });
```

### What you'll keep coming back to

| Pattern                          | Where                                                                      |
| -------------------------------- | -------------------------------------------------------------------------- |
| The SDK methods you already know | Each guide reuses `brain.ask`, `brain.pay`, `brain.approve`, `brain.proof` |
| Idempotency keys                 | Required on every mutating call; retries are free                          |
| Trace IDs                        | Returned on every response; paste into the Console for the full timeline   |
| Webhooks                         | Subscribe once, get notified on the events you care about                  |


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