Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/tmux-python/libtmux-mcp/testing-mcp-with-cli-agentsnpx skills add tmux-python/libtmux-mcp --skill testing-mcp-with-cli-agentsgit clone --depth 1 https://github.com/tmux-python/libtmux-mcpWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00181 | $0.03999 |
| Opus 5 | $0.00090 | $0.01999 |
| Sonnet 5 | $0.00036 | $0.00800 |
| Haiku 4.5 | $0.00018 | $0.00400 |
Grade A, and why
testing-mcp-with-cli-agents scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 287 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing an MCP server through real CLI agents
Unit tests prove the server's internals; they don't prove a real agent can discover a tool, get past its approval gate, call it, and survive cancelling it mid-flight. This skill exercises that whole path by pointing installed CLI agents at a checkout and driving them — with the tmux tool surface (libtmux-mcp) as the running example, though the shape generalizes to any MCP server.
The core idea: three tmux servers, never one
The single biggest mistake is running everything on one tmux socket. Keep three distinct servers, each on its own socket, and the whole thing becomes safe and observable:
| Role | Socket | Who touches it | Why separate |
|---|---|---|---|
| Your real session | default | you, interactively | must never be mutated by a test |
| Harness | tmux -L cli-harness |
the driver: send-keys prompts in, capture-pane render out |
isolates the CLI TUI you're driving |
| MCP-target | tmux -L mcp-target, exported as LIBTMUX_SOCKET=mcp-target to the server |
the MCP server, when the agent calls tmux tools | independent ground-truth; a destructive tool here can't kill the agent you're driving |
The server resolves its socket from LIBTMUX_SOCKET and runs tmux -L <name>
(src/libtmux_mcp/_utils.py builds argv with -L server.socket_name, defaulted
from that env var). Exporting LIBTMUX_SOCKET=mcp-target into the server's
config env fully sandboxes every tmux tool call onto a scratch server.
Pre-create it so the agent has something to see:
$ tmux -L mcp-target new-session -d -s scratch
Keeping harness separate from MCP-target is the load-bearing part: if the
agent's own TUI pane lived on the socket its MCP server mutates, one
kill-server / kill-session tool call would tear down the agent mid-test, and
your captures would be polluted by the agent's own UI redraws.
Climb only as high as the question needs — three fidelity layers
Layer 0 — Direct MCP smoke, no CLI at all
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 287 lines · 181 tokens per session scan A faa9a702a3c2
testing-mcp-with-cli-agents is a skill published in the GitHub repository tmux-python/libtmux-mcp (12 stars, last pushed 2d ago), licensed MIT. It adds 181 tokens to every session and 3,999 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
intuitive-port-worktree
Port changes from one git worktree or checkout into the default repository folder's current branch, then by default sync the result to the remote default branch when everything is clean. Use when the user asks to move, copy, transfer, transplant, cherry-pick, apply a patch, or port worktree changes into the…
comparative-synthesis
Compare and synthesize findings across multiple completed DeepScan reports. Use when the user wants cross-run analysis, trend comparison, or a unified summary from several research sessions.
research-briefing
Build a focused literature and citation briefing from PapersFlow. Use when the user wants paper search, citation verification, related-paper discovery, or citation graph exploration.
citation-verifier
Verify, normalize, and enrich a single citation or paper identifier. Use when the user pastes a DOI, URL, arXiv ID, PubMed ID, citation string, or paper title and wants it checked.
deepscan-monitor
Run and monitor PapersFlow DeepScan jobs. Use when the user wants long-running research progress, intermediate findings, final reports, or plotting from a completed run.
git-guardrails-claude-code
Set up Claude Code hooks to block dangerous git commands (push, reset --hard, clean, branch -D, etc.) before they execute. Use when user wants to prevent destructive git operations, add git safety hooks, or block git push/reset in Claude Code.