Compatibility Issue with Gemini CLI: 'Invalid tool name' errors when loading agents

[xilu0]

When using Gemini CLI (v0.41.2, darwin), the ExtensionManager fails to load the agents in the caveman extension.

Error Log:

[ExtensionManager] Error loading agent from caveman: Failed to load agent from ~/.gemini/extensions/caveman/agents/cavecrew-builder.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
tools.3: Invalid tool name
tools.4: Invalid tool name

Observations:
The agents (cavecrew-builder.md, cavecrew-investigator.md, cavecrew-reviewer.md) define their tools using Claude Code's naming conventions (e.g., [Read, Edit, Write, Grep, Glob]).
Gemini CLI's ExtensionManager validates these tool names. Since Gemini CLI uses different tool names (e.g., read_file, replace, write_file, grep_search, glob), it rejects these agents as invalid.

Expected Behavior:
The extension should provide compatible tool names for the Gemini CLI environment or include a mapping layer.

Environment:

• macOS (darwin)
• Gemini CLI v0.41.2

[ehurrn]

Adding impact & following...

 % uname -v
Darwin Kernel Version 25.5.0: Mon Apr 27 20:41:26 PDT 2026; root:xnu-12377.121.6~2/RELEASE_ARM64_T8132

 % gemini -v    
0.42.0

% gemini extensions install https://github.com/JuliusBrussee/caveman
Installing extension "caveman".
This extension will append info to your gemini.md context using GEMINI.md

Agent Skills:

This extension will install the following agent skills:

  * caveman-stats: Show real token usage and estimated savings for the current session. Reads directly from the Claude Code session log — no AI estimation. Triggers on /caveman-stats. Output is injected by the mode-tracker hook; the model itself does not compute the numbers.

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman-stats/SKILL.md) (2 items in directory)

  * caveman-review: Ultra-compressed code review comments. Cuts noise from PR feedback while preserving the actionable signal. Each comment is one line: location, problem, fix. Use when user says "review this PR", "code review", "review the diff", "/review", or invokes /caveman-review. Auto-triggers when reviewing pull requests.

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman-review/SKILL.md) (2 items in directory)

  * caveman-help: Quick-reference card for all caveman modes, skills, and commands. One-shot display, not a persistent mode. Trigger: /caveman-help, "caveman help", "what caveman commands", "how do I use caveman".

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman-help/SKILL.md) (2 items in directory)

  * caveman-compress: Compress natural language memory files (CLAUDE.md, todos, preferences) into caveman format to save input tokens. Preserves all technical substance, code, URLs, and structure. Compressed version overwrites the original file. Human-readable backup saved as FILE.original.md. Trigger: /caveman-compress FILEPATH or "compress memory file"

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman-compress/SKILL.md) (4 items in directory)

  * caveman-commit: Ultra-compressed commit message generator. Cuts noise from commit messages while preserving intent and reasoning. Conventional Commits format. Subject ≤50 chars, body only when "why" isn't obvious. Use when user says "write a commit", "commit message", "generate commit", "/commit", or invokes /caveman-commit. Auto-triggers when staging changes.

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman-commit/SKILL.md) (2 items in directory)

  * caveman: Ultra-compressed communication mode. Cuts token usage ~75% by speaking like caveman while keeping full technical accuracy. Supports intensity levels: lite, full (default), ultra, wenyan-lite, wenyan-full, wenyan-ultra. Use when user says "caveman mode", "talk like caveman", "use caveman", "less tokens", "be brief", or invokes /caveman. Also auto-triggers when token efficiency is requested.

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/caveman/SKILL.md) (2 items in directory)

  * cavecrew: Decision guide for delegating to caveman-style subagents. Tells the main thread WHEN to spawn `cavecrew-investigator` (locate code), `cavecrew-builder` (1-2 file edit), or `cavecrew-reviewer` (diff review) instead of doing the work inline or using vanilla `Explore`. Subagent output is caveman-compressed so the tool-result injected back into main context is ~60% smaller — main context lasts longer across long sessions. Trigger: "delegate to subagent", "use cavecrew", "spawn investigator/builder/reviewer", "save context", "compressed agent output".

    (Source: /var/folders/y_/s_lvq4wx5ks7s7x2fh9t1h480000gn/T/gemini-extensionktu1dG/skills/cavecrew/SKILL.md) (2 items in directory)


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[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/ehurrn/.gemini/extensions/caveman/agents/cavecrew-builder.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
tools.3: Invalid tool name
tools.4: Invalid tool name
[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/ehurrn/.gemini/extensions/caveman/agents/cavecrew-investigator.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
tools.3: Invalid tool name
[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/ehurrn/.gemini/extensions/caveman/agents/cavecrew-reviewer.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
Extension "caveman" installed successfully and enabled.

[ericethridge]

Adding my sentiment. Still getting this error in Gemini CLI:

❯ gemini extensions install https://github.com/JuliusBrussee/caveman
[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/-------/.gemini/extensions/caveman/agents/cavecrew-builder.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
tools.3: Invalid tool name
tools.4: Invalid tool name
[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/--------/.gemini/extensions/caveman/agents/cavecrew-investigator.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
tools.3: Invalid tool name
[ExtensionManager] Error loading agent from caveman: Failed to load agent from /Users/-------/.gemini/extensions/caveman/agents/cavecrew-reviewer.md: Validation failed: Agent Definition:
tools.0: Invalid tool name
tools.1: Invalid tool name
tools.2: Invalid tool name
Extension "caveman" is already installed. Please uninstall it first.

[alaa-alghazouli]

I've submitted a PR that fixes the tools schema format which was likely causing these 'Invalid tool name' errors. It also addresses related Opencode installation and configuration bugs.

PR: #452