# Dynamic Data Sources (RPC)

Sources provide dynamic dropdown options in action forms. Define them at the miniapp root level under `source`, and reference them in parameters via `x-source`.


```javascript
// MiniApp root level
source: {
  // Each key must start with "rpc_"
  rpc_channels_list: {
    url: 'https://slack.com/api/conversations.list?limit=1000&types=public_channel,private_channel',
    method: 'GET',
    headers: {
      Authorization: 'Bearer [[accessToken]]',
    },
    dataPath: 'channels',         // JSONPath to the array in the response
    valueField: 'id',             // Field to use as the option value
    labelField: 'name',           // Field to use as the option label
  },

  rpc_users_list: {
    url: 'https://slack.com/api/users.list?limit=1000',
    method: 'GET',
    headers: {
      Authorization: 'Bearer [[accessToken]]',
    },
    dataPath: 'members',
    valueField: 'id',
    labelField: 'profile.real_name',  // Supports nested paths
  },
},

// Then reference from action parameters:
actions: [{
  parameters: {
    properties: {
      channel: {
        type: 'string',
        title: 'Channel',
        'x-source': 'rpc_channels_list',  // ← Matches key in source
        'x-fallback': 'input',
      },
    },
  },
}]
```

**Source definition fields:**

| Field | Type | Required | Description |
|  --- | --- | --- | --- |
| `url` | string | ✅ | API endpoint URL (supports `[[cred]]` placeholders) |
| `method` | string | ✅ | HTTP method (`GET` or `POST`) |
| `headers` | object | — | Request headers |
| `queryParams` | object | — | Additional query parameters |
| `dataPath` | string | ✅ | Path to the array in the API response |
| `valueField` | string | ✅ | Field name to use as the option value |
| `labelField` | string | ✅ | Field name to use as the option label |
| `valueFields` | object | — | Alternative value fields per `sourceRef` context |


**How it works at runtime:**

1. User opens the action form
2. Frontend calls `miniAppsActionSources` GraphQL query with the `sourceKey`
3. Backend fetches the source URL with the user's credentials injected
4. Response array is extracted from `dataPath`
5. Each item is mapped to `{ value, label }` using `valueField` and `labelField`
6. Dropdown renders with the options