/**
 * Poll-http source evaluator.
 *
 * GETs the URL; the observation is `<status>\n<body>` so a status flip OR a body
 * change both register as a diff. Uses the built-in fetch (Node 22+).
 */
import type { MonitorSource } from '../config.js';
import type { Observation } from './types.js';
/** GET the source URL and return status + body as the observation. */
export declare function evaluate(source: MonitorSource): Promise<Observation | null>;
