# Feature flag
LLMS index: [llms.txt](/llms.txt)
---
- [Feature Flag Attributes](#feature-flag-attributes)
- [Deprecated Feature Flag Attributes](#deprecated-feature-flag-attributes)
## Feature Flag Attributes
This document defines attributes for Feature Flags.
**Attributes:**
| Key | Stability | Value Type | Description | Example Values |
| --- | --- | --- | --- | --- |
| `feature_flag.context.id` |  | string | The unique identifier for the flag evaluation context. For example, the targeting key. | `5157782b-2203-4c80-a857-dbbd5e7761db` |
| `feature_flag.error.message` |  | string | A message providing more detail about an error that occurred during feature flag evaluation in human-readable form. | `Unexpected input type: string`; `The user has exceeded their storage quota` |
| `feature_flag.key` |  | string | The lookup key of the feature flag. | `logo-color` |
| `feature_flag.provider.name` |  | string | Identifies the feature flag provider. | `Flag Manager` |
| `feature_flag.result.reason` |  | string | The reason code which shows how a feature flag value was determined. | `static`; `targeting_match`; `error`; `default` |
| `feature_flag.result.value` |  | any | The evaluated value of the feature flag. [1] | `#ff0000`; `true`; `3` |
| `feature_flag.result.variant` |  | string | A semantic identifier for an evaluated flag value. [2] | `red`; `true`; `on` |
| `feature_flag.set.id` |  | string | The identifier of the [flag set](https://openfeature.dev/specification/glossary/#flag-set) to which the feature flag belongs. | `proj-1`; `ab98sgs`; `service1/dev` |
| `feature_flag.version` |  | string | The version of the ruleset used during the evaluation. This may be any stable value which uniquely identifies the ruleset. | `1`; `01ABCDEF` |
**[1] `feature_flag.result.value`:** With some feature flag providers, feature flag results can be quite large or contain private or sensitive details.
Because of this, `feature_flag.result.variant` is often the preferred attribute if it is available.
It may be desirable to redact or otherwise limit the size and scope of `feature_flag.result.value` if possible.
Because the evaluated flag value is unstructured and may be any type, it is left to the instrumentation author to determine how best to achieve this.
**[2] `feature_flag.result.variant`:** A semantic identifier, commonly referred to as a variant, provides a means
for referring to a value without including the value itself. This can
provide additional context for understanding the meaning behind a value.
For example, the variant `red` maybe be used for the value `#c05543`.
---
`feature_flag.result.reason` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.
| Value | Description | Stability |
| --- | --- | --- |
| `cached` | The resolved value was retrieved from cache. |  |
| `default` | The resolved value fell back to a pre-configured value (no dynamic evaluation occurred or dynamic evaluation yielded no result). |  |
| `disabled` | The resolved value was the result of the flag being disabled in the management system. |  |
| `error` | The resolved value was the result of an error. |  |
| `split` | The resolved value was the result of pseudorandom assignment. |  |
| `stale` | The resolved value is non-authoritative or possibly out of date |  |
| `static` | The resolved value is static (no dynamic evaluation). |  |
| `targeting_match` | The resolved value was the result of a dynamic evaluation, such as a rule or specific user-targeting. |  |
| `unknown` | The reason for the resolved value could not be determined. |  |
## Deprecated Feature Flag Attributes
Describes deprecated feature flag attributes.
**Attributes:**
| Key | Stability | Value Type | Description | Example Values |
| --- | --- | --- | --- | --- |
| `feature_flag.evaluation.error.message` | 
Replaced by `feature_flag.error.message`. | string | Deprecated, use `feature_flag.error.message` instead. | `Flag `header-color` expected type `string` but found type `number`` |
| `feature_flag.evaluation.reason` | 
Replaced by `feature_flag.result.reason`. | string | Deprecated, use `feature_flag.result.reason` instead. | `static`; `targeting_match`; `error`; `default` |
| `feature_flag.provider_name` | 
Replaced by `feature_flag.provider.name`. | string | Deprecated, use `feature_flag.provider.name` instead. | `Flag Manager` |
| `feature_flag.variant` | 
Replaced by `feature_flag.result.variant`. | string | Deprecated, use `feature_flag.result.variant` instead. | `red`; `true`; `on` |
---
`feature_flag.evaluation.reason` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.
| Value | Description | Stability |
| --- | --- | --- |
| `cached` | The resolved value was retrieved from cache. |  |
| `default` | The resolved value fell back to a pre-configured value (no dynamic evaluation occurred or dynamic evaluation yielded no result). |  |
| `disabled` | The resolved value was the result of the flag being disabled in the management system. |  |
| `error` | The resolved value was the result of an error. |  |
| `split` | The resolved value was the result of pseudorandom assignment. |  |
| `stale` | The resolved value is non-authoritative or possibly out of date |  |
| `static` | The resolved value is static (no dynamic evaluation). |  |
| `targeting_match` | The resolved value was the result of a dynamic evaluation, such as a rule or specific user-targeting. |  |
| `unknown` | The reason for the resolved value could not be determined. |  |