Evaluation API

Use the evaluation API when you cannot use the Workers binding. The API accepts query parameters or a JSON request body.

The GET endpoint accepts context attributes as query parameters. Use it for scalar context values.

Flagship coerces unambiguous number and boolean query values. For example, 42 becomes a number and true becomes a boolean. Other values remain strings.

JSON-looking query values remain strings. A value such as {"plan":"enterprise"} does not create a nested object.

Use POST to send nested objects, arrays, or null. The following request evaluates new-checkout with structured context:

curl "https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/flagship/apps/$APP_ID/evaluate" \
	--request POST \
	--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
	--json '{
		"flagKey": "new-checkout",
		"context": {
				"targetingKey": "user-42",
				"profile": {
						"plan": "enterprise"
				},
				"tags": [
						"beta"
				]
		}
	}'

The POST response contains the same fields as GET:

{
	"flagKey": "new-checkout",
	"value": true,
	"variant": "on",
	"reason": "TARGETING_MATCH"
}

Invalid context returns a 400 response. Refer to Limits and evaluation error codes for details.