Gemini Grounding MCP

Give Claude Code and other MCP clients current Google Search results through the Gemini API - with inline citation markers and a numbered source list under every answer.

Use it when an assistant needs web-grounded research instead of relying on training data alone. It builds on nothing but the official @google/genai and @modelcontextprotocol/sdk packages, pinned to exact versions.

Scope of use: research queries only. Not intended for production workloads or for connecting to sensitive systems.

What it offers

• Citations you can check. Markers such as [1] sit in the answer text, numbered to match the source list below it. A marker can be missing, but it is never placed where the API does not support it - so an unmarked sentence is a reason to look closer.
• The queries Gemini actually ran. The footer lists what was typed into Google, which answers what no source list can: whether the search covered your question at all.
• Token usage for every call, split into input, output and thinking tokens. What they cost is on Google's pricing page.
• Model and thinking level are yours to set. Both persist, both can be overridden for a single request, and both are read at call time, so a change applies to the next answer rather than after a client restart. The thinking level is the main lever on how many tokens a query consumes.
• Failures stay visible. An answer cut off at the token limit or stopped by a filter is marked as such, dropped citation markers are counted, and a failing model returns an error instead of a quiet switch to a different one.
• Search, URL Context and Code Execution in one call. Gemini can read a page you name and run code; if it did, the code and its output are part of the answer. The only instruction the server adds is today's date - what gets researched follows from your question.
• A command line tool on the same core. Verify your API key and model choice before registering the server, and read the full error text when a call fails.

What an answer looks like

Question: "Which Node.js version is currently LTS?"

The current Node.js release versions are as follows [1]:

* Latest LTS: v24.18.1 (recommended for most users)
* Latest Current release: v26.5.1

Sources:
[1] nodejs.org - https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQG52u...

---
🔢 30 input / 86 output / 0 thinking tokens | 🔍 1 sources | 🤖 gemini-flash-latest (thinking: minimal)
🔎 Searched: Node js latest LTS version

The redirect URL is abbreviated here for readability; the real output carries it in full.

Quick start

Nothing to install up front: the client starts the server through npx, which fetches the package on first use and caches it - only that first call takes a few seconds longer. A permanent install is optional and mainly of interest for the command line tool (see Installing globally).

1. Set your API key

The key is passed exclusively through the GEMINI_API_KEY environment variable, never in code and never in the config file. It has to be set persistently, before the client starts the server.

Windows (PowerShell, user scope, once):

[Environment]::SetEnvironmentVariable('GEMINI_API_KEY', '<your-api-key>', 'User')

Reopen the shell afterwards so the variable is available.

macOS / Linux - add to ~/.zshrc, ~/.bashrc or equivalent:

export