> For the complete documentation index, see [llms.txt](https://docs.lingoql.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lingoql.com/sub0/apis-abi/structure.md).

# Structure

A Sub0 endpoint is a resource with one or more actionables.

The resource defines the API surface.

The actionables define what happens when it runs.

### Endpoint shape

```json
{
  "id": "user-signup-01",
  "resource": "user-signup",
  "tokenize": {
    "type": "JWT",
    "encryption_key": "$ENV.JWT_KEY"
  },
  "actionables": [
    {
      "id": 1,
      "mode": "QUERY",
      "sql_query": {
        "query": "INSERT INTO users (email) VALUES ($1)",
        "parameters": ["email"]
      }
    }
  ],
  "returnables": ["id", "email", "token"]
}
```

### Core endpoint properties

| Property                        | Purpose                                  |
| ------------------------------- | ---------------------------------------- |
| `id`                            | Unique endpoint ID                       |
| `resource`                      | Route name                               |
| `maintenance`                   | Temporarily disables the endpoint        |
| `tokenize`                      | Issues a token                           |
| `protected`                     | Requires a valid token                   |
| `cacheable`                     | Caches the response                      |
| `queue`                         | Queues the whole resource                |
| `parallel`                      | Runs actionables concurrently            |
| `run_in_background`             | Returns before work completes            |
| `returnables`                   | Controls the final response              |
| `combine_returned_results_from` | Merges results from selected actionables |
| `actionables`                   | Lists the operations to run              |

### Core actionable properties

| Property                      | Purpose                                    |
| ----------------------------- | ------------------------------------------ |
| `id`                          | Unique actionable ID inside the resource   |
| `mode`                        | `QUERY`, `HTTPREQUEST`, or `UPLOAD`        |
| `sql_query`                   | SQL operation                              |
| `mongo_query`                 | MongoDB operation                          |
| `http`                        | External HTTP request                      |
| `uploads`                     | File upload rules                          |
| `payload_validation`          | Request validation                         |
| `hashables`                   | Hash fields before use                     |
| `verify_hashables`            | Verify hashed values                       |
| `generators`                  | Generate IDs and similar values            |
| `depends_on`                  | Reuse outputs from other actions           |
| `returnables`                 | Fields to return from this action          |
| `main_returnable`             | Marks the primary response                 |
| `cacheable`                   | Caches this action                         |
| `queue`                       | Queues this action                         |
| `retries`                     | Retries failed execution                   |
| `broadcast_websocket_message` | Emits a WebSocket message                  |
| `cron_job`                    | Schedules the action                       |
| `no_op`                       | Runs only when called through `depends_on` |

### Execution modes

#### `QUERY`

Use `sql_query` for SQL databases.

Use `mongo_query` for MongoDB.

#### `HTTPREQUEST`

Use this to call third-party APIs or internal services.

```json
"mode": "HTTPREQUEST",
"http": {
  "url": "https://api.example.com",
  "method": "POST",
  "headers": {},
  "request_body": {}
}
```

#### `UPLOAD`

Use this for file uploads and file deletion.

```json
"mode": "UPLOAD",
"uploads": {
  "max_file_uploads": 1,
  "allowed_mimetypes": ["image/png"]
}
```

### Response shaping

Use `returnables` to control what comes back to the client.

```json
"returnables": [
  "name",
  "email",
  "address.city",
  "users.0.name"
]
```

Rules:

* Dot notation reads nested fields.
* Array indices are supported.
* `"ignore:field"` excludes a field.

If you do not set `main_returnable`, Sub0 returns the last actionable result by default.

### How execution works

* Actionables run in order by default.
* Set `parallel: true` only when actions do not depend on each other.
* Use `depends_on` when one action needs another action's output.

### Next step

Move to [Accessors](/sub0/apis-abi/accessors.md) to see how values are resolved at runtime.


---

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