Search within one YouTube channel using YouTube's native channel search, not global search or local filtering of the channel's latest videos. Pass a handle with or without @ and a keyword query. Results can include videos, Shorts, live streams and playlists in separate collections. Keep the same handle and query when passing the previous response's continuationToken. Stop when continuationToken is null; passing the literal continuationToken=null returns an uncharged terminal response. Each successful page costs 1 credit, including pages with no matches; invalid requests and retrieval failures Uses the caller's OpenAny gateway credentials. Charges and authorization are determined by the gateway.