gemini-advisor

A Claude Code Mod that gives the model a Gemini advisor it calls by itself. The model writes what it did, what it is about to do and its question; Gemini reads the whole conversation so far, tool calls and outputs included, and answers with a second opinion that comes back as the tool result.

The idea follows the advisor tool of the Claude API, where the executor model calls a stronger model that reads its transcript. This mod asks Gemini instead, and the model also sends a message of its own.

What it does

1. At session start, while it is on, the mod declares the tool mcp__gemini-advisor__advise with one input, message.
2. The engine lists a plugin's tool behind ToolSearch, where the model sees only its name (measured on 2.1.277). So the mod adds a # Gemini advisor note to the end of the env_info_simple section of the system prompt: what the tool does, how to load it, and when to call it. The note does not change during a session, so the prompt cache holds.
3. The note makes the call required, without the user asking, at four moments: before a substantial change or a multi-step plan, when stuck (the same error twice), when choosing between two approaches, and before saying the work is done. It also tells the model to check the advice against the code.
4. At a call, the mod reads the conversation with $.session.messages(), which includes the running turn (measured), renders every message and each tool call with its input and output, and sends it with the model's message in one generateContent request. Above 2,000,000 characters the longest outputs are cut to their head and tail first. gemini-core builds the request with the key, the model and the thinking level it holds for gemini-advisor, and reads the answer.
5. The advice comes back as the tool result. Any failure comes back as an error result that says why, so the model sees it; nothing is swallowed.
6. Gemini answers HTTP 503 ("high demand") now and then, and the next request often works (measured: 2 of 5 requests on two flash models). As gemini-core reads it, the mod asks again after 1 s, 2 s and 3 s, at most four times, and starts no attempt once 40 s have passed, so the last one fits the 60-second tool timeout.

In a live check on 2.1.277 with gemini-3.8-flash, the model called the advisor on its own while choosing between two approaches, sent 27 messages (15k tokens), got the advice in 7.1 seconds, and its answer used the advice. With a softer note ("call it on your own") the model did not call it in two such turns, and said afterwards that the turn was one the note named.

What it shows

A toast after each advice, and the last one in /gemini-advisor:

gemini-advisor: asked gemini-3.8-flash · 27 messages · 15k in, 2k out · sent to Gemini free tier

The tool row in the transcript holds the model's message and the advice (ctrl+o).

Command

/gemini-advisor              on or off, the model, thinking level and tier gemini-core holds, whether a key is set, the last advice
/gemini-advisor on | off     on is refused while gemini-core has no key; off: a call answers that the advisor is off
/gemini-advisor reset        off again, the default

The advisor is off after an install: the model gets no tool and no note, and nothing is sent to Gemini. on declares the tool at once. The system prompt note follows the setting at /clear or the next session, not at once, because a change of the system prompt in the middle of a session makes the next request write the whole prompt cache again. After off the note leaves at /clear or the next session and the tool at the next session; until then a call answers that the advisor is off.

The key, the tier, the model (default gemini-3.8-flash) and the thinking level are gemini-core's, and a change applies from the next call:

/gemini-core model advisor gemini-3.7-flash
/gemini-core thinking advisor high
/gemini-core paid

Free tier or paid tier

Every call sends the conversation: your prompts, the commands the model ran and the contents of the files it read. On the free tier Google may use them and human reviewers may read them; the gemini-core README quotes the Gemini API Additional Terms. On a project you would not show to Google, use a key with billing enabled and set /gemini-core paid.

With the free key used in the live check, gemini-3.1-pro-preview answered HTTP 429 (quota exceeded), so a pro model needs a paid key.

Install

claude plugin marketplace add KilimcininKorOglu/claude-code-mods
claude plugin install gemini-advisor@kilimcininkoroglu-mods

It depends on gemini-core, which claude plugin install adds. Function hooks are early access. Nothing loads without the flag. To keep it on, add this to ~/.claude/settings.json:

{ "env": { "CLAUDE_CODE_ENABLE_FUNCTION_HOOKS": "1" } }

After installing

1. Set the Gemini key and the tier in gemini-core, as its After installing section says, then restart Claude Code.
2. Run /gemini-advisor on, then /clear or start a new session, so the system prompt note reaches the model. Without a key on answers still off: gemini-core has no Gemini key and stays off.
3. Run /gemini-advisor. The first line reads on · <model> · thinking ... · <tier> tier · key set.
4. When an advice call fails with Gemini HTTP 429, the model has no quota on your key. Pick another with /gemini-core model advisor.

After an update from 0.1.x: claude plugin update does not add gemini-core (measured on 2.1.278), so run claude plugin install gemini-core@kilimcininkoroglu-mods once. Version 0.2.0 moved the key, tier and model to gemini-core; the apiKey, tier and model options and the settings /gemini-advisor free|paid|model stored before are no longer read, so set them again in gemini-core. Version 0.3.0 made the advisor off by default: after an update from an earlier version it is off unless you ran /gemini-advisor on before, so run /gemini-advisor on once.

Options

What it can reach

Validated with claude plugin validate on Claude Code 2.1.278:

❯ ./register.ts hooks: session.start, classic.SessionStart, command.run{command=gemini-advisor}, prompt.section{name=env_info_simple}, tool.call{tool=mcp__gemini-advisor__advise}
❯ ./register.ts calls: $.clock.now (via askGemini), $.clock.sleep (via askGemini), $.command.register, $.gemini.enroll, $.gemini.read (via askGemini), $.gemini.request (via askGemini), $.gemini.settings (via runCommand, storeEnabled), $.http.fetch (via askGemini), $.session.messages (via conversation), $.store.delete (via runCommand), $.store.get (via isEnabled), $.store.set (via storeEnabled), $.tool.register (via declareTool), $.ui.toast (via advise)

Reach L3, reaches the network.

1. Reads:    the conversation at each advisor call (messages, tool inputs and outputs); its own $.store; from gemini-core, the request with the key
2. Runs:     no process; while on, it adds one note to the system prompt and declares one tool
3. Sends:    the conversation and the model's message, one request per call (up to four after a 503, and once more per extra key after a 429 or a key error), to the URL gemini-core builds (generativelanguage.googleapis.com) with the key in the x-goog-api-key header, never in the URL
4. Persists: in $.store, the on/off setting; the last usage line lives in memory
5. Hostile input: the advice is untrusted text the model reads as a tool result, so a hostile or wrong advice can steer the model as text in a file it reads can; the note tells the model to check it

Limits

• Whether the model calls the advisor is its own decision. The live check covered one kind of turn.
• The tool description names no model. The engine keeps the description it first sent for the whole session: a tool registered again after a model change still reached the model with the old text (measured on 2.1.278). The toast and /gemini-advisor name the model a call went to.
• The engine serves the tool with a 60-second MCP timeout (debug log, 2.1.277). A call that takes longer fails, and the model reads the error.
• The note is added to the env_info_simple section. A setup whose system prompt has no such section gets no note, and the model sees the tool's name only. Only one setup was checked.
• A subagent's call sends only its message, because which transcript $.session.messages() answers inside a subagent was not verified.
• $.session.messages() answers the newest 4096 messages of a long transcript.
• Every call sends the whole conversation, so a long session makes each call larger and slower.

Development

make install     # eslint, typescript-eslint, typescript
make lint        # complexity limit 10, fails the build above it
make typecheck   # needs .claude/types/ from /plugin-types
make validate
make test        # claude plugin test