The closest alternative to Gemini 3.1 Pro Preview Custom Tools is Gemini 3.5 Flash — comparable intelligence (43.3 vs —); for a cheaper option, Qwen3.7 Max runs $1.25/M vs $2.00/M; for more speed, Relace Apply 3 hits 3.1k t/s; and the best open-weight substitute is MiniMax M3.
Gemini 3.5 Flash is the closest alternative to Gemini 3.1 Pro Preview Custom Tools, with an Intelligence Index of 43.3 (Gemini 3.1 Pro Preview Custom Tools scores —) at $1.50 per million input tokens.
Yes — Qwen3.7 Max costs $1.25 per million input tokens versus $2.00 for Gemini 3.1 Pro Preview Custom Tools, while staying within ~8 points of its Intelligence Index.
MiniMax M3 is the strongest open-weight alternative to Gemini 3.1 Pro Preview Custom Tools — downloadable from Hugging Face and self-hostable, scoring 54.7 on intelligence.