pr-review example ships tools.core: [] which disables all MCP tools since gemini-cli v0.41.0 – workflow green but no review posted

[philwatt]

TL;DR

The examples/workflows/pr-review example ships with:

"tools": {
  "core": []
}

Since gemini-cli v0.41.0 (google-gemini/gemini-cli#25720), any tools.core value – including the empty array – makes the policy engine emit a wildcard * DENY that statically excludes every MCP tool from the tool registry, even in YOLO mode and even with the MCP server trusted/allowed. That means the example as shipped disables the github-mcp-server the workflow depends on: the model receives no MCP tool declarations, blind-guesses tool names until maxSessionTurns is exhausted (Tool "<name>" not found. Did you mean "activate_skill"?), and – because the CLI exits 0 with the error only embedded in JSON stdout – the workflow stays green while posting no review.

Full root-cause analysis with source references at gemini-cli v0.50.0 (policy priorities, PolicyEngine.getExcludedTools(), repro, verified workarounds) is in the upstream report: google-gemini/gemini-cli#28361.

Expected behavior

Deploying the pr-review example as documented produces a PR review.

Observed behavior

Green workflow run, no review posted. Logs show the MCP server's tools being discovered (Refresh for 'github' discovered 3 tools) but none callable; the run ends in FatalTurnLimitedError inside the JSON stdout with exit code 0. (That the action treats this as success is #519; the extension's stale hard-coded tool names, #510, make the blind-guessing loop even less likely to accidentally recover.)

Suggested fix

Until/unless the upstream policy behaviour changes, the example settings should allowlist what the workflow actually needs. Verified working end-to-end:

"tools": {
  "core": [
    "activate_skill",
    "mcp_github_*"
  ]
}

or equivalently "tools": { "allowed": ["mcp_github_*"] } plus "core": ["activate_skill"]. Note activate_skill must be allowlisted explicitly – the code-review extension's mandatory skill activation is a built-in tool call that "core": [] also denies.

Environment

• google-github-actions/run-gemini-cli with the pr-review example as shipped (gemini-cli-extensions/code-review extension, github-mcp-server v0.27.0)
• gemini-cli v0.50.0, GitHub Actions ubuntu-latest, non-interactive mode, GEMINI_API_KEY auth