Flag routes: evaluate · StartupBuilder

Reference for Flag, one group of Flag routes.

Flag.evaluate

Evaluate returns the Variant a Flag assigns one unit, the same one every time, and records the Exposure with every option and its propensity. Verb page.

Text

POST /{namespace}/flags/{flag}/evaluate

Path: flag. Body, as JSON: the other inputs. Emits Flag.evaluated.

Inputs

Input	Type	Required	Description
`flag`	Flag	required	The Flag to evaluate, by key.
`unit`	`string`	required	The id of the Visitor, Customer, Contact, Conversation or request being assigned.
`default`	`string`		The Variant key returned when the Flag is off or the value may not be varied.

Returns

Output	Type	Required	Description
`variant`	Variant	required	The Variant assigned to the unit.
`exposure`	Exposure		The Exposure recorded; none in Mode try.

Refuses when

Check	Error	Fix	Then call
The key is valid, but its scopes do not allow this operation.	`forbidden`	Use a key whose scopes cover the operation, or ask an owner of the namespace to grant them.	None.

Example

Terminal

curl -X POST https://api.sb/leaseline.app/flags/flag_1YJLhjTlfx/evaluate \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"unit":"Example unit"}'

JSON

{
  "api": "https://api.sb/leaseline.app",
  "variant": {
    "$id": "https://api.sb/leaseline.app/variants/variant_nvdfmt7dTw",
    "$type": "Variant",
    "key": "Example key",
    "value": {}
  },
  "exposure": {
    "$id": "https://api.sb/leaseline.app/exposures/exposure_Ua2Xw4KsJB",
    "$type": "Exposure",
    "unit": "Example unit",
    "options": {},
    "propensity": 1,
    "at": "2026-10-22T12:00:00Z"
  },
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/act_br07HsG8MG",
    "operation": "Flag.evaluate",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/leaseline.app/actions/act_br07HsG8MG"
  }
}

Flag.evaluateCopy Anchor Link

Flag.evaluate