Mcp Client

Spawn and interact with MCP (Model Context Protocol) servers via JSON-RPC stdio. Use when the user wants to call tools from MCP servers that are configured in OpenClaw config (~/.openclaw/openclaw.json or ~/.openclaw/config.yaml) but the runtime does not natively expose them. Covers stdio, SSE, and streamable-http transports. Use for: file operations via desktop-commander, browser automation via playwright-mcp, memory storage via server-memory, database queries via supabase-mcp, or any other MCP server the user has installed.

Deepak Vaid@space-cadet

Install

openclaw skills install @space-cadet/mcp-client

MCP Client Skill

Purpose

OpenClaw versions before native MCP client support (e.g. 2026.3.13) do not expose configured MCP servers as agent tools. This skill bridges that gap by spawning MCP server processes directly and speaking JSON-RPC over stdio.

When to use

User asks to use an MCP server (desktop-commander, playwright, memory, etc.)
openclaw mcp list returns "unknown command" or config path not found
Native MCP tool calling is unavailable in the current runtime

When NOT to use

Native MCP support is already working (openclaw mcp list shows servers)
The task can be done with existing agent tools (exec, read, edit, browser)

Workflow

1. Discover configured servers

Read ~/.openclaw/openclaw.json (JSON) or ~/.openclaw/config.yaml (YAML) and extract mcp.servers:

json

{
  "mcp": {
    "servers": {
      "desktop-commander": {
        "command": "node",
        "args": ["/Users/deepak/code/mcps/desktop-commander/dist/index.js"]
      },
      "memory": {
        "command": "npx",
        "args": ["-y", "@modelcontextprotocol/server-memory"],
        "env": { "MEMORY_FILE_PATH": "/Users/deepak/.memory/memory.json" }
      }
    }
  }
}

2. Spawn the server process

Use scripts/mcp-call.js (see below) or inline Node.js to:

Spawn the process with command + args
Set any env variables
Send initialize request (JSON-RPC)
Send tools/list to discover available tools
Send tools/call to invoke the desired tool
Parse the result and return to user
Kill the process

3. Handle responses

MCP servers return results as JSON-RPC responses. Tool results are in:

json

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "content": [{"type": "text", "text": "..."}],
    "isError": false
  }
}

Extract result.content[0].text for text output, or handle isError: true.

Helper Script

Use scripts/mcp-call.js for reliable MCP communication:

bash

node scripts/mcp-call.js <server-name> <tool-name> '<json-args>'

Examples:

bash

# Read a file via desktop-commander
node scripts/mcp-call.js desktop-commander read_file '{"path":"/Users/deepak/code/mcps/desktop-commander/package.json","length":10}'

# Read memory graph
node scripts/mcp-call.js memory read_graph '{}'

# Search memory nodes
node scripts/mcp-call.js memory search_nodes '{"query":"physics"}'

The script:

Reads server config from ~/.openclaw/openclaw.json
Spawns the process, sends initialize + tools/call
Outputs clean result text (or JSON if --json)
Exits with code 1 on error

Memory MCP Server Tools

The @modelcontextprotocol/server-memory exposes a knowledge graph:

Tool	Purpose
`create_entities`	Add entities with type + observations
`create_relations`	Link entities with relation types
`add_observations`	Append observations to existing entities
`read_graph`	Dump the full graph
`search_nodes`	Search entities by name/observation
`open_nodes`	Get specific entities by name
`delete_entities`	Remove entities
`delete_observations`	Remove specific observations
`delete_relations`	Remove relations

Security Notes

Only spawn servers from trusted config (user-owned ~/.openclaw/)
Respect allowedDirectories in desktop-commander — it will reject paths
Do not log or echo MCP server env vars (may contain tokens)
Kill processes after use to avoid zombie MCP servers

Current Limitations

Stdio transport only (no SSE/streamable-http support in workaround)
One-shot calls (no persistent MCP connection across agent turns)
Process spawn overhead per call (~1-2s for feature flag fetch)
Tool schemas are discovered dynamically, not cached

Future

When OpenClaw natively supports MCP clients (openclaw mcp list works), this skill becomes obsolete. Transition path: remove skill, rely on native bundle-mcp tool profile.