# build

URL: /business/nouns/startup/build · Id: `verb:Startup.build` · Call: `await $.Startup.build({ … })` (SDK) or the `do` tool at `https://api.sb/mcp`. Inputs says what to pass, Outputs what returns, When it waits who approves.

> Build provisions the Systems, Sites and Interfaces a Startup’s definition declares, and moves the Startup to Building.

Build provisions the [Systems](/business/nouns/system), [Sites](/business/nouns/site) and [Interfaces](/business/nouns/interface) a [Startup](/business/nouns/startup)’s definition declares, and moves the Startup to Building.

## Inputs
| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `startup` | [Startup](/business/nouns/startup) | Yes | The Startup to build. |

## Outputs
| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `startup` | [Startup](/business/nouns/startup) | Yes | The Startup, now Building. |

## Effects
- Emits [`Startup.built`](/business/events/Startup.built).
- Performed by the [Engineering Lead](/agents/engineering/engineering-lead).
- Provisions every System the Startup’s Templates include.
- Moves the Startup from Idea to Building.

## Refuses when
| Check | Error | Fix | Then call |
| --- | --- | --- | --- |
| Template chosen (`building-template`) | [`refused`](/code/api/errors/refused) | Name a Startup Template in the definition. | [Startup.update](/business/nouns/startup/update) |
| Problem stated (`building-problem`) | [`refused`](/code/api/errors/refused) | Write the problem slot with its workarounds and why now. | [Hypothesis.create](/business/nouns/hypothesis/create) |
| Brand named (`building-brand`) | [`refused`](/code/api/errors/refused) | Give the Brand a name, a voice, a logo, and a theme. | [Brand.update](/business/nouns/brand/update) |
| Products declared (`building-products`) | [`refused`](/code/api/errors/refused) | Set the kind of every Product. | [Product.update](/business/nouns/product/update) |
| Three slots at Commitment (`building-slots`) | [`refused`](/code/api/errors/refused) | Run the cheapest test on each slot below Commitment, such as a reserve deposit. | [Experiment.start](/business/nouns/experiment/start) |
| The key is valid, but its scopes do not allow this operation. | [`forbidden`](/code/api/errors/forbidden) | Use a key whose scopes cover the operation, or ask an owner of the namespace to grant them. | [Startup.build](/business/nouns/startup/build) |

## When it waits
| Gate | Default |
| --- | --- |
| Decision class | Low: two-way, nothing at stake |
| [Delay window](/systems/trust-and-governance/controls/one-way-windows) | None: it runs once review passes. |
| Limit | The call [Limit](/business/nouns/limit) of the [Permission](/business/nouns/permission) it runs under. |
| Over the Limit | It waits `pending` for an [Approval](/business/nouns/approval) from the [Founder](/agents/founding/founder). Approved, it runs; refused, it ends `refused` with [`limit-exceeded`](/code/api/errors/limit-exceeded); unanswered by its deadline, it ends `canceled`. |

## Example

**Ask**

```text
Build RouteWise.
```

**API**

```bash
curl -X POST https://api.sb/routewise.dev/startups/startup_1/build \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY"
```

```json
{
  "api": "https://api.sb/routewise.dev",
  "startup": {
    "$id": "https://api.sb/routewise.dev/startups/startup_1",
    "$type": "Startup",
    "name": "RouteWise"
  },
  "action": {
    "$id": "https://api.sb/routewise.dev/actions/action_1",
    "operation": "Startup.build",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/routewise.dev/actions/action_1"
  }
}
```

**SDK**

```ts
import { $ } from 'startup-builder'

const startup = await $.Startup.build({ startup: 'startup_1' })
```

**CLI**

```bash
npx startup-builder do Startup.build --json '{"startup":"startup_1"}'
```

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Startup.build({ startup: 'startup_1' })"
  }
}
```

Guides that call it: [Start a business](/business/start-a-business), [Turn my app into a business](/start/guides/turn-my-app-into-a-business).