mcarcaso/mcp-client

MCP Client

Use this skill when another skill declares an mcp: block, or when you need to inspect/call a remote/stdIO MCP server without wiring it globally into Vito.

This is a generic MCP bridge. Individual skills should declare where to connect; this skill discovers the current tool list live via MCP tools/list, so tool schemas can evolve without stale docs.

Supported MCP Config

In another skill's SKILL.md frontmatter:

---
name: tavily
description: Web research through Tavily MCP
mcp:
  transport: http              # http | streamable-http | stdio
  url: https://mcp.example.com/mcp?apiKey=${API_KEY}
  # Optional safety/config:
  allowToolPrefix: tavily_     # optional; soft safety fence for calls
  timeoutMs: 30000             # optional; default 30000, max 120000
  maxOutputBytes: 50000        # optional; default 50000
---

For stdio servers:

mcp:
  transport: stdio
  command: npx
  args: ["-y", "@vendor/mcp-server"]
  env:
    API_KEY: ${API_KEY}

Secrets are resolved from process.env first, then user/secrets.json. Never hardcode raw secrets in skill files.

Commands

node src/skills/builtin/mcp-client/mcp-client.mjs list <skill-md-or-url-or-dir>
node src/skills/builtin/mcp-client/mcp-client.mjs call <skill-md-or-url-or-dir> <tool_name> '<json_args>'
node src/skills/builtin/mcp-client/mcp-client.mjs batch <skill-md-or-url-or-dir> '<json_steps>'
node src/skills/builtin/mcp-client/mcp-client.mjs schema <skill-md-or-url-or-dir> <tool_name>

Aliases:

• tools = list
• invoke = call
• sequence = batch

Examples

Discover tools from a skill with an mcp: block:

node src/skills/builtin/mcp-client/mcp-client.mjs list user/skills/tavily/SKILL.md

Call a discovered tool:

node src/skills/builtin/mcp-client/mcp-client.mjs call user/skills/tavily/SKILL.md tavily_search '{"query":"Forrest Frank Nashville GEODIS Park tickets","max_results":5}'

Call multiple tools over one MCP connection/session — useful for browser MCP servers where state matters:

node src/skills/builtin/mcp-client/mcp-client.mjs batch user/skills/playwright/SKILL.md '[{"tool":"browser_navigate","args":{"url":"https://example.com"}},{"tool":"browser_snapshot","args":{}}]'

Use a raw remote MCP URL directly:

node src/skills/builtin/mcp-client/mcp-client.mjs list 'https://mcp.example.com/mcp?apiKey=${API_KEY}'

Output

• list returns current tool names, descriptions, and input schemas.
• schema returns one tool's input schema.
• call returns the MCP tool result content as JSON, with text/resource/image blocks preserved.
• batch returns an array of step results from one shared MCP connection.

Safety Rules

• Always run list before the first call unless you just listed tools in the same task.
• If the target skill declares allowTools or allowToolPrefix, respect it.
• Keep outputs capped. If output is truncated, narrow the query or call a more specific tool.
• For tools that send messages, emails, calls, payments, bookings, account changes, or other real-world actions: confirm with Mike first.
• Do not use untrusted MCP URLs unless Mike explicitly approves the server.