feat(skill): enable advanced MCP tool use with mcpx

[cs50victor]

Summary

Adds mcpx as a builtin skill providing lightweight MCP tool access via CLI.

What mcpx provides:

• On-demand tool discovery without loading all schemas upfront (zero token cost)
• Daemon mode for stateful operations (browser automation, database transactions)
• Simple CLI interface: mcpx server/tool '{"args": ...}'

Pain points addressed:

Issue	Problem	How mcpx helps
#882	MCP startup takes 2-3 minutes	Daemon mode provides instant tool availability
#878	Tools show connected but not exposed	Reliable discovery via mcpx / mcpx grep
#949	No way to prefer custom tools	mcpx grep "*pattern*" enables tool selection

Changes

• Added mcpxSkill to src/features/builtin-skills/skills.ts
• Skill includes:
  • Quick reference for common commands
  • Daemon mode documentation for stateful operations
  • Decision tree for when to use daemon vs direct calls
  • Anti-patterns section

Test plan

• bun run typecheck passes
• Manual testing: invoke skill via /skill mcpx in OpenCode

Note

mcpx is available at: https://github.com/cs50victor/mcpx

Install: brew install cs50victor/tap/mcpx or bun install -g mcpx

---

Summary by cubic

Adds mcpx as a builtin skill to discover and invoke MCP tools via a simple CLI, with a daemon mode for stateful workflows. Improves tool availability and selection, addressing #882 (startup delay), #878 (tools not exposed), and #949 (tool preference).

• New Features
  • Added mcpxSkill to builtin skills for on-demand MCP tool discovery without schema preload (zero token cost).
  • Supports daemon mode for persistent state (browser automation, database transactions).
  • Includes quick command reference, decision tree, and anti-patterns in the skill template.
  • Enables reliable tool search and selection via grep.

^{Written for commit 58a659c. Summary will update on new commits.}

[github-actions]

All contributors have signed the CLA. Thank you! ✅
_{Posted by the CLA Assistant Lite bot.}

[cs50victor]

I have read the CLA Document and I hereby sign the CLA

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

---

Since this is your first cubic review, here's how it works:

• cubic automatically reviews your code and comments on bugs and improvements
• Teach cubic by replying to its comments. cubic learns from your replies and gets better over time
• Ask questions if you need clarification on any suggestion

[code-yeongyu]

Thank you for this contribution! I need some time to think about whether this approach aligns with the project direction. Will get back to you soon.

[cs50victor]

sounds good, i personally switched to using the cli for all mcps and haven't found a reason to switch back since.

[code-yeongyu]

Thank you for this contribution!

I've reviewed the PR and decided to close it for the following reasons:

1. Architecture mismatch: The skills structure has been refactored to use separate files (skills/index.ts), while this PR adds the mcpx skill inline to skills.ts, making it incompatible with the current codebase.

2. Conflicting state: The PR is in CONFLICTING status and would require significant rebasing to merge with the current dev branch.

3. External dependency: mcpx is a third-party CLI tool that requires manual installation (brew or bun install -g), which adds friction for users. The project prefers native solutions.

4. Progress on pain points:

   • [Bug]: Context7 and Grep_app MCP takes 3 mins to connect. And user msg cannot be sent out before MCP connection timeout! #882 (startup delay) is now closed
   • [Question]: How to suggest what tool to use ? #949 (tool preference) is closed
   • Only [Bug]: context7 MCP connected but tools not exposed to agents #878 (tools not exposed) remains open, which is being addressed through native MCP improvements

5. Alternative implementations: The project now has:

   • Native MCP integration with improvements (feat(mcp-oauth): add full OAuth 2.1 authentication for MCP servers #1169, fix: prevent builtin MCPs from overwriting user MCP configs #956)
   • dev-browser skill (feat(skills): add agent-browser option for browser automation #1090) for stateful browser operations
   • Unified Claude Tasks system (Implement unified Claude Tasks system with single multi-action tool #1356) for better orchestration

The mcpx CLI approach doesn't align with the project's direction of building native, integrated solutions rather than relying on external CLI tools.

Feel free to reopen if you'd like to discuss an alternative approach that integrates natively or if you have questions about the decision.

[cs50victor]

understandable. Appreciate the feedback.