Gemini MCP

gemini-mcp

MCP server for Google Gemini media generation. Exposes thirteen tools to Claude over stdio: list available models, generate/edit/compose images, generate a consistent set of images from a master prompt, multi-turn image refinement (Interactions API), video generation (omni), music generation (Lyria), an async result poll for long generations, and Files API upload/list/delete for reusable image references. Output is written to disk by default (path returned) or returned inline as base64. Built on the Gemini v1beta API (generativelanguage.googleapis.com) using the Nano Banana / Nano Banana Pro (images), omni (video), and Lyria (music) model families.

Developed and maintained by AI (Claude Code).

Environment Variables

Confirmations

Sending a local file to Google (the images / master_images / video_path inputs, or gemini_upload_file's path) and every delete ask for confirmation first. A client that can show a confirmation prompt (Claude Code) gets the real prompt, unless MCP_CONFIRM_ELICITATION=off. Elsewhere the first call does nothing and returns a preview (the resolved local paths with their MIME types and sizes, or the method/path being deleted) plus a confirmToken; only a repeat call with the same arguments and that token proceeds. The token is single-use, expires, and is bound to the exact arguments — a changed prompt or a swapped file between the two calls is refused. Pure text prompts, URLs, files/ references and base64 inputs are not gated.

Long generations and client timeouts

4K / Pro-model generations can outrun an MCP host's own tools/call timeout (error -32001). The server sends notifications/progress heartbeats so hosts that reset their timeout on progress wait it out. If the host still gives up, the server-side generation usually completes anyway: the image is written to the output dir, gemini_interact also writes an .json sidecar recording the interaction_id, and continue_last: true resumes the interaction the lost response belonged to.

When a chained call 404s

A 404 on a request carrying previous_interaction_id is not proof the chain expired. The only 404 body observed live is generic — "Requested entity was not found." — and never names *which* entity. An unknown or renamed model id, and an expired Files API `files/…` uri (~48h TTL), return exactly the same thing. So the server no longer asserts a cause it can't establish: the upstream text is surfaced verbatim, and gemini_interact runs an experiment to find out which it was.

Most often the id isn't missing at all — it just isn't *visible* yet. The interactions store is eventually consistent, and a freshly created id can 404 while the same id resolves fine minutes later; heavy turns (4K, Pro, thinking_level: high) are the likeliest to hit it, which is exactly the turn you most want to chain from. So a chained 404 is retried with exponential backoff for up to 120s (GEMINI_CHAIN_RETRY_MS) before anything is declared broken. The 404 generates nothing and isn't billed, so the wait costs only time.

After that budget is spent, the tool looks up that id's sidecar, re-attaches the image it produced, and re-issues the request without the chain:

• The re-issue succeeds → the chain really was the problem, and you get your image anyway, reported as chain_recovered: { expired_interaction_id, reanchored_on }. The 404'd attempt generates nothing, so this costs the one generation you'd have paid for re-anchoring manually.
• The re-issue 404s too → the interaction id was never the cause. You get told exactly that, with the upstream text, and pointed at the model id and any files/… uri instead of being sent to chase an interaction that was fine all along.
• No sidecar matches the dead id → the original error, rather than a guess. Re-anchoring on the wrong picture would silently corrupt the edit.

Separately, continue_last no longer dies with the server process: with no in-memory id it resumes from the newest .json sidecar in the output dir and reports continued_from_sidecar: true. That case was never an expired chain at all — the interaction was alive upstream the whole time; only our memory of its id was gone.

For hosts whose timeout can't be tamed (e.g. Claude Desktop, a fixed ~30s cap that ignores progress), two guards make re-issuing safe and unnecessary:

• `async: true` returns a job_id immediately instead of the image, so the call can't time out at all; poll gemini_get_result with the job_id until it's done.
• `idempotency_key` makes a repeat call idempotent — a retry with the same key returns the recorded result (reused: true) instead of billing a second generation. (Even without a key, two identical in-flight calls are deduplicated automatically.)

Tools

Generation tools also share three throughput/latency controls: async: true (return a job_id immediately), max_wait_ms (wait up to a budget, then hand back the job_id — fast results stay in-band, slow batches never trip the host timeout), and idempotency_key (a retry returns the recorded result instead of re-billing). On a hosted deployment, a gemini_image_set result with more than one image also carries a `bundle_url` — one sig