Use for keyword research, SEO/content ideas, query expansion before /v1/web or /v1/news, or guessing what people search for around a topic ("how to la" -> "how to lay tile", …). Returns the completions in source order. lang sets the suggestion language (en, de, fr, es, ja, …). Primary source Google's public suggest endpoint, fallback DuckDuckGo autocomplete; the response names the source used. No suggestions = 404, not charged. Paid tool: x402 USDC on Base, $0.001 per successful call; call without payment to receive the PaymentRequired object.