Autocomplete Google Ads keyword themes

<Info>This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.</Info>

Suggests keyword themes as someone types, for the keyword picker on a Smart campaign.

Returns matching theme names from Google's catalog, most relevant first, and never more than limit. Anything the caller types is still valid to save, so treat these as suggestions rather than the allowed set.

A query shorter than two characters returns an empty list rather than an error, because a one-character prefix matches too much to be useful. country_code scopes the catalog and is required in practice: Google returns nothing without one, so leaving it unset uses US.

language_code is best-effort. Google's catalog covers a fixed set of languages, and anything outside it falls back to English rather than failing, so a request for an unsupported language returns English themes with no signal that the substitution happened. Send a two-letter code; a regional tag like pt-BR is reduced to its first part.

An empty list also means Google was briefly unreachable, so treat "no suggestions" as "nothing to show right now" rather than "this word has no themes".

<Note>This endpoint accepts a personal API key. Workspace API keys are not authorized for it and are rejected with a 403.</Note>