# relate

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

> Relate links two Things by a Relationship their Nouns declare, readable from both ends at once.

Relate links two [Things](/business/nouns/thing) by a [Relationship](/business/nouns/relationship) their [Nouns](/business/nouns/noun) declare, readable from both ends at once.

## Inputs
| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `thing` | [Thing](/business/nouns/thing) | Yes | The source Thing. |
| `predicate` | `string` | Yes | The Relationship as read from the source, such as `places`. |
| `to` | [Thing](/business/nouns/thing) | Yes | The target Thing. |

## Outputs
| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `relationship` | [Relationship](/business/nouns/relationship) | Yes | The Relationship, with its provenance. |
| `thing` | [Thing](/business/nouns/thing) | Yes | The Thing the Relationship starts from. |

## Effects
- Emits [`Thing.related`](/business/events/Thing.related).
- Performed by the [Data Engineer](/agents/engineering/data-engineer).
- Two-way: it runs at once, in the `try`, `send` and `do` modes.
- Refuses a predicate that neither Noun declares.
- On a to-one Relationship, replaces the old target; the old link stays in history.

## Refuses when
| Check | Error | Fix | Then call |
| --- | --- | --- | --- |
| 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. | [Thing.relate](/business/nouns/thing/relate) |
| A predicate that neither Noun declares | [`refused`](/code/api/errors/refused) | Clear what the check names, then call it again. | [Thing.relate](/business/nouns/thing/relate) |

## 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
Relate the latest thing.
```

**API**

```bash
curl -X POST https://api.sb/shiftnote.app/things/thing_1/relate \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"predicate":"Example predicate","to":"thing_1"}'
```

```json
{
  "api": "https://api.sb/shiftnote.app",
  "relationship": {
    "$id": "https://api.sb/shiftnote.app/relationships/relationship_1",
    "$type": "Relationship",
    "predicate": "Example predicate",
    "inverse": "Example inverse"
  },
  "thing": {
    "$id": "https://api.sb/shiftnote.app/things/thing_1",
    "$type": "Thing",
    "id": "Example id",
    "type": [
      "noun_1"
    ]
  },
  "action": {
    "$id": "https://api.sb/shiftnote.app/actions/action_1",
    "operation": "Thing.relate",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/shiftnote.app/actions/action_1"
  }
}
```

**SDK**

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

const { relationship, thing } = await $.Thing.relate({ thing: 'thing_1', predicate: 'Example predicate', to: 'thing_1' })
```

**CLI**

```bash
npx startup-builder do Thing.relate --json '{"thing":"thing_1","predicate":"Example predicate","to":"thing_1"}'
```

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Thing.relate({ thing: 'thing_1', predicate: 'Example predicate', to: 'thing_1' })"
  }
}
```