Agent Skill

nxv ships an Agent Skills-standard skill that lets AI coding agents — Claude Code, OpenAI Codex CLI, Pi, OpenClaw, GitHub Copilot CLI, Cursor, Gemini CLI, Amp, Goose, and anything else that reads SKILL.md — run nxv commands on your behalf without extra setup. The nxv binary embeds the skill and installs it for you.

What is a skill?

A skill is a SKILL.md file (with optional supporting files) that teaches an agent how to use a tool. When the skill is loaded, the agent knows every subcommand, flag, JSON output shape, and HTTP endpoint for nxv. It can answer questions like "which nixpkgs commit shipped python 2.7?" or "give me the nix shell command for nodejs 15" by running the right nxv invocation (or hitting the public API) and interpreting the result.

Installing the skill

The nxv skill subcommand generates and installs the skill from a single embedded template:

# Install user-wide for every agent detected on this machine
nxv skill install

# Install into the current project (.claude/skills + .agents/skills,
# which every supported agent reads at project level)
nxv skill install --project

# Install for specific agents only
nxv skill install claude codex

# Install for every supported agent, detected or not
nxv skill install --all

# See supported agents, their paths, and what's installed where
nxv skill list

A user-wide install (the default) targets agents whose config directory exists under your home directory. Per agent, the skill lands in <skills dir>/nxv/SKILL.md:

Agent	User-wide	Project-level
claude	~/.claude/skills/	.claude/skills/
codex	~/.codex/skills/	.agents/skills/
pi	~/.pi/agent/skills/	.pi/skills/
openclaw	~/.openclaw/skills/	.agents/skills/
copilot	~/.copilot/skills/	.github/skills/
cursor	~/.cursor/skills/	.agents/skills/
gemini	~/.gemini/skills/	.agents/skills/
amp	~/.config/amp/skills/	.agents/skills/
goose	~/.config/goose/skills/	.agents/skills/
agents	~/.agents/skills/	.agents/skills/

The agents target is the generic cross-agent directory from the Agent Skills standard — most tools read it, so it also serves as the fallback when no agents are detected.

The table shows each agent's primary directory — the one nxv skill install <agent> writes to. Several agents read additional locations: Copilot reads .github/skills/, .claude/skills/, or .agents/skills/ in a repository, and Pi reads .agents/skills/ as well as .pi/skills/. That is why the default project install writes only the .claude + .agents pair: every supported agent picks up one of the two.

To remove installed skills:

nxv skill uninstall            # Remove from every user-wide agent path
nxv skill uninstall --project  # Remove project-level installs

Manual install (no nxv binary)

Fetch the canonical copy straight from the repository:

mkdir -p ~/.claude/skills/nxv
curl -sL https://raw.githubusercontent.com/utensils/nxv/main/.claude/skills/nxv/SKILL.md \
  -o ~/.claude/skills/nxv/SKILL.md

Using the skill

Once installed, agents that support slash-command invocation can call it directly:

/nxv search python 2.7
/nxv info python311 3.11.4
/nxv history nodejs_15

Or just ask naturally — the agent loads the skill automatically when your question matches its description:

"Which nixpkgs commit had python 2.7?"

"Give me the nix shell command for nodejs 15.14."

"When was ruby 2.6 last in nixpkgs?"

You don't need a local index for the skill to be useful — agents can hit the public API at https://nxv.urandom.io directly, or you can set NXV_API_URL=https://nxv.urandom.io in your environment so the CLI uses the hosted instance transparently.

For agents

The skill is designed so autonomous agents can extract structured data reliably. The search, info, and history subcommands support --format json, and every data-returning HTTP API response is wrapped in a stable { "data": ... } envelope (plus meta for paginated lists; only the operational /health and /metrics endpoints are unwrapped). Agents should:

1. Run nxv <subcommand> --format json (CLI) or hit /api/v1/... (HTTP) for machine-readable output.
2. Pipe to jq (or parse in-process) for the specific field they need.
3. Never rely on the human-readable table output — column widths and formatting are terminal-dependent.

Example agent pattern — generate a nix shell invocation for a specific version directly from the public API:

curl -s "https://nxv.urandom.io/api/v1/packages/python27/versions/2.7.18/first" | \
  jq -r '.data | "nix shell nixpkgs/\(.first_commit_hash | .[0:7])#\(.attribute_path)"'

Or via the CLI against any backend:

nxv search nodejs 15 --exact --format json | \
  jq -r '.[0] | "nix shell nixpkgs/\(.first_commit_hash | .[0:7])#\(.attribute_path)"'

Keeping the skill up to date

The installed skill is byte-identical to the template embedded in your nxv binary, so refreshing it is just upgrading nxv and reinstalling:

nxv update           # Get the latest nxv (also refreshes the index)
nxv skill install    # Rewrite the installed skills from the new binary

Skill source

The canonical template lives at src/skill/SKILL.md in the repository; the checked-in copies under .claude/skills/ and .agents/skills/ are generated from it.