Google announced on February 19 2026 that the Gemini 3.1 Pro Preview model is now available through the Gemini API. The update adds a separate endpoint – gemini‑3.1‑pro‑preview‑customtools – that gives the model a stronger ability to prioritize custom tools, such as bash scripts, when developers mix them with built‑in functions. The model sits in the newer Gemini 3 series, positioned after the Gemini 3 Pro Preview that was retired in March.
What changed for developers?
The new endpoint means developers can keep using the same API call style but tell the model to favor their own tools over the default ones. Google says this helps when a workflow needs precise control over external commands or when a project uses a mix of shell scripts and the API’s built‑in capabilities. Existing Gemini 3 Pro Preview users are automatically pointed to the 3.1 version, so no code changes are required unless they want the custom‑tools behavior.
Why it matters
For everyday developers, the new model gives more reliable control when mixing their own scripts with the API’s built‑in tools, reducing surprises in automated workflows. Existing users keep their access without changing code, but can opt in for the custom‑tools endpoint to fine‑tune how the model runs external commands.
