Agent-Skills.md

Agent Skills: ARC skill: mcp

Connect MCP clients (`arc mcp`), negotiate local vs remote capability, and explore the live AFS tool surface.

UncategorizedID: arcblock/agent-skills/mcp

Repository

arcblock/agent-skills
ArcBlockLicense: MIT
51

Install this agent skill to your local

pnpm dlx add-skill https://github.com/ArcBlock/agent-skills/tree/HEAD/plugins/arc/skills/mcp

Skill Files

Browse the full folder contents for mcp.

Download Skill

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plugins/arc/skills/mcp/SKILL.md

Skill Metadata

Name
"mcp"
Description
"Connect MCP clients (`arc mcp`), negotiate local vs remote capability, and explore the live AFS tool surface."

ARC skill: mcp

MCP is a transport into the same AFS world, not a second ontology.

Capability negotiation (local first)

Decide which MCP path is available before assuming tools exist:

| Host situation | What to do | |---|---| | arc CLI is on PATH | Use local stdio: plugin .mcp.json server arc-local → arc mcp (bridge to the daemon; starts it if needed). | | arc CLI is not on PATH | Plugin skills still load. Do not treat this as a silent total failure. Install the CLI (curl -fsSL https://arc.afsd.io/install.sh \| bash — see docs/guides/arc-cli-distribution.md). Plugin bootstrap that auto-installs CLI is S5 (not shipped yet). | | Want remote / no-shell host | Not ready in v1. arc-remote is intentionally absent from .mcp.json so "not configured" is not the same colour as "endpoint down". Tracked in #6432 (hosted endpoint + OAuth grant). |

Say the remote path is unready out loud. An agent that reads "remote unavailable" behaves differently from one that never sees remote mentioned.

Distinguish failure reasons when local MCP will not start:

  • arc missing — command not found / spawn ENOENT for arc. Fix: install CLI (above). Message shape: needs arc on PATH.
  • arc present but daemon unreachable — CLI runs; bridge cannot attach / daemon will not stay up. Fix: arc service start (or check instance). Message shape: daemon unavailable — not "arc missing".

Connect

# Bridge stdio MCP client ↔ running daemon (auto-starts daemon if configured to)
arc mcp

# Standalone serve variants exist under `arc serve --transport mcp-*`
# Check: arc serve --help

After connect (L1)

Prefer live AFS tools over re-reading booklets. For multi-terminal layout pointers:

arc skill show afs   # section: WM / multi-terminal

Plugin .mcp.json (v1 — local only, flat format — no mcpServers wrapper):

{
  "arc-local": { "command": "arc", "args": ["mcp"] }
}

Claude Desktop user config (outside the plugin) still uses the mcpServers envelope:

{
  "mcpServers": {
    "AFS": { "command": "arc", "args": ["mcp"] }
  }
}

Agent discipline

  • Use MCP explore / tools to discover live mounts and tools after connect.
  • Do not treat MCP tool lists as a substitute for offline arc skill bootstrap.
  • Mutations still go through AFS semantics (path write/exec) with the same safety expectations.
  • If MCP initialize fails, read this skill's negotiation table — do not invent a remote server entry.

Related

  • Offline bootstrap: arc skill list
  • Daemon: arc skill show daemon
  • Path ops: arc skill show afs
  • Remote MCP (deferred): GitHub issue #6432