> For the complete documentation index, see [llms.txt](https://docs.abtasty.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.abtasty.com/server-side/command-line-interface/resource-loader/feature-experimentation/flag.md).

# Flag

#### Definition

A **Flag** is a governed feature toggle/config key your application reads at runtime. Variations set flag values via **modifications** (e.g., `"type": "FLAG"` in a variation). Declaring flags centrally enforces naming, typing, and reuse across campaigns.

#### Payload Properties

When creating or updating a flag, the `payload` can include:

* **`id`** (String, *optional*) – The flag's unique ID. Include this only when updating an existing flag.
* `name` (String, **required**) — Unique flag key used in `modifications.value`.
* `type` (String, **required**) — Expected value type (e.g., `"string"`, `"boolean"`, `"number"`, `"json"`).
* `description` (String, optional) — Human-readable description.
* `source` (String, optional) — Origin of the flag (e.g., `"manual"`, `"api"`).
* `default_value` (Any, optional) — Default value returned when no override/experiment applies.
* `predefined_values` (Array, optional) — Allowed values (for enums or UI pickers). Leave empty for free-form types.

> Notes\
> • Keep `type` consistent with the values you plan to set in variations.\
> • Use `predefined_values` to constrain inputs (e.g., `["blue","green"]`) when you want UI validation.

**Example Project Payload:**

```json
{
  "name": "flag_created_with_resource_loader",
  "type": "string",
  "description": "Loaded from resource loader",
  "source": "manual",
  "default_value": "",
  "predefined_values": []
}
```

#### Response Fields

When a Flag is returned by the API/Resource Loader, you’ll receive server-managed metadata plus the normalized definition:

* `id` (String) — Unique flag identifier.
* `name` (String) — Flag key.
* `type` (String) — Value type (e.g., `"string"`).
* `description` (String) — Description.
* `source` (String) — Origin (e.g., `"manual"`).
* `default_value` (Any) — Default value when no overrides apply.
* `predefined_values` (Array) — Allowed values, if any.
* `created_at` (String, ISO-8601) — Creation timestamp.

**Example Response**

```json
{
  "created_at": "2025-11-12T11:26:43+00:00",
  "default_value": "",
  "description": "Loaded from resource loader",
  "id": "flag_id",
  "name": "flag_created_with_resource_loader",
  "predefined_values": [],
  "source": "manual",
  "type": "string"
}
```

#### Error Codes

* **InvalidPayload** – Missing project name when creating a project, or other payload formatting issues.
* **PermissionDenied** – User not allowed to create projects (if such permission is restricted).


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.abtasty.com/server-side/command-line-interface/resource-loader/feature-experimentation/flag.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.