MCP Adapter (OpenClaw Plugin)

🔧 Fixed Fork: This is a fixed version of androidStern-personal/openclaw-mcp-adapter that resolves the multi-agent tool registration issue.

Exposes MCP (Model Context Protocol) server tools as native OpenClaw agent tools.

Instead of running MCP servers through a CLI skill, this plugin connects to your MCP servers at startup, discovers their tools, and registers each one as a first-class tool that agents can invoke directly.

🆕 What's Fixed

Original Issue: MCP tools were only available to the main agent, not to other agents.

Root Cause: The plugin registered tools as static objects instead of factory functions, preventing proper per-agent tool instantiation.

Fix: Changed tool registration to use factory functions that are called for each agent:

// ❌ Before: Static object (only works for main agent)
api.registerTool({
  name: toolName,
  description: "...",
  parameters: {...},
  async execute(id, params) {...}
})

// ✅ After: Factory function (works for all agents)
api.registerTool(
  (ctx) => ({
    name: toolName,
    description: "...",
    parameters: {...},
    async execute(id, params) {...}
  }),
  { name: toolName }
)

Now MCP tools are properly available to all agents in your OpenClaw setup.

Requirements

• OpenClaw gateway
• Node.js 18+
• MCP servers you want to connect to

Installation

# Install from this fixed fork
openclaw plugins install https://github.com/laozuzhen/openclaw-mcp-adapter.git

Alternative: install from source

git clone https://github.com/laozuzhen/openclaw-mcp-adapter.git
openclaw plugins install ./openclaw-mcp-adapter

Configuration

1. Enable the plugin and configure servers

Add to ~/.openclaw/openclaw.json:

{
  "plugins": {
    "entries": {
      "mcp-adapter": {
        "enabled": true,
        "config": {
          "servers": [
            {
              "name": "myserver",
              "transport": "stdio",
              "command": "npx",
              "args": ["-y", "some-mcp-server"],
              "env": {
                "API_KEY": "${MY_API_KEY}"
              }
            }
          ]
        }
      }
    }
  }
}

2. Allow for sandboxed agents

Add "mcp-adapter" to your sandbox tool allowlist:

{
  "tools": {
    "sandbox": {
      "tools": {
        "allow": ["group:runtime", "group:fs", "mcp-adapter"]
      }
    }
  }
}

3. Restart the gateway

openclaw gateway restart

4. Verify

openclaw plugins list
# Should show: MCP Adapter | mcp-adapter | loaded

Server Configuration

Stdio transport (spawns a subprocess)

{
  "name": "filesystem",
  "transport": "stdio",
  "command": "npx",
  "args": ["-y", "@anthropic/mcp-filesystem", "/path/to/dir"],
  "env": {
    "SOME_VAR": "value"
  }
}

HTTP transport (connects to a running server)

{
  "name": "api",
  "transport": "http",
  "url": "http://localhost:3000/mcp",
  "headers": {
    "Authorization": "Bearer ${API_TOKEN}"
  }
}

Config Options

Option	Type	Default	Description
servers	array	[]	List of MCP servers to connect to
toolPrefix	boolean	true	Prefix tool names with server name (e.g., myserver_toolname)

Server Options

Option	Type	Required	Description
name	string	Yes	Unique name for this server
transport	"stdio" | "http"	No	Connection type (default: stdio)
command	string	stdio only	Command to spawn
args	string[]	No	Command arguments
env	object	No	Environment variables
url	string	http only	Server URL
headers	object	No	HTTP request headers

Environment Variable Interpolation

Use ${VAR_NAME} in env and headers values to reference environment variables from ~/.openclaw/.env:

{
  "env": {
    "API_KEY": "${MY_SERVICE_API_KEY}"
  }
}

How It Works

1. On gateway startup, the plugin connects to each configured MCP server
2. Calls listTools() to discover available tools
3. Registers each tool with OpenClaw using its name, description, and JSON Schema
4. When an agent invokes a tool, the plugin proxies the call to the MCP server
5. If the connection dies, it automatically reconnects on the next tool call

Example: AgentMail

{
  "name": "agentmail",
  "transport": "stdio",
  "command": "npx",
  "args": ["-y", "agentmail-mcp"],
  "env": {
    "AGENTMAIL_API_KEY": "${AGENTMAIL_API_KEY}"
  }
}

This registers tools like agentmail_create_inbox, agentmail_send_email, etc.

License

MIT