# `Challenge.serialize` Serializes a challenge to the WWW-Authenticate header format. ## Usage ```ts twoslash import { Challenge } from 'mppx' const challenge = Challenge.from({ id: 'abc123', realm: 'mpp.dev', method: 'tempo', intent: 'charge', request: { amount: '1000000', currency: '0x...', recipient: '0x...' }, }) const header = Challenge.serialize(challenge) // @log: 'Payment id="abc123", realm="mpp.dev", method="tempo", intent="charge", request="eyJhbW91bnQiOi..."' ``` ## Return type ```ts type ReturnType = string ``` A string suitable for the WWW-Authenticate header value. The serialized string includes optional fields when present: `description`, `digest`, `expires`, and `opaque` (server-defined correlation data set via `meta` in `Challenge.from`). ## Parameters ### challenge * **Type:** `Challenge` The challenge to serialize.