Expose (JSON-RPC Proxy) MCP server for AI agents

The MCP server "Expose" allows you to build custom tools that integrate with the Claude desktop app through the Model Context Protocol. It provides a streamlined way to create and deploy self-hosted tools that can be invoked directly from Claude's interface.

Installation

Setting Up the Environment

Install the Expose CLI tool:

curl -fsSL https://github.com/a0dotrun/expose/releases/download/stable/download_cli.sh | bash

Install the required dependencies:
```
npm i @a0dotrun/expose
```

Creating Your MCP Server

Basic Server Setup

Create a new server file:

touch src/server.ts

Add the following code to initialize a basic server:

// src/server.ts
import { create } from "@a0dotrun/expose"

const app = create({
  tools: [],
})

export default {
  port: 3000,
  fetch: app.fetch,
}

Adding Custom Tools

Extend your server by defining tools with appropriate schemas and functionality:

// src/server.ts
import { create } from "@a0dotrun/expose"
import { tool } from "@a0dotrun/expose/tool"
import { z } from "zod"

// Define a tool to get subscription information
const getCustomerSubscription = tool({
  name: "getCustomerSubscription",
  description: "Get subscription information for a customer",
  args: z.object({
    customer: z.string().uuid()
  }),
  run: async (input) => {
    // Your subscription logic here
    return input;
  },
});

// Define a tool to create subscriptions
const createCustomerSubscription = tool({
  name: "createCustomerSubscription",
  description: "Create a subscription for a customer",
  args: z.object({
    customer: z.string().uuid()
  }),
  run: async (input) => {
    // Your subscription logic here
    return input;
  },
});

const app = create({
  tools: [
    getCustomerSubscription,
    createCustomerSubscription,
  ],
});

export default {
  port: 3000,
  fetch: app.fetch,
}

Running Your Server

Start your server locally for testing:

npm run dev

You can also deploy the server to a public URL for production use.

Integrating with Claude Desktop

Registering Your Server

To make your tools available in the Claude desktop application:

Locate the Claude desktop MCP configuration file:
- On macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Update the configuration to include your MCP server:

{
  "mcpServers": {
    "subscriptionManager": {
      "command": "/Users/acmeuser/.local/bin/expose-cli",
      "args": ["--url", "http://localhost:3000", "--timeout", "15"]
    }
  }
}

Note: Replace http://localhost:3000 with your public URL if you've deployed the server.

Usage Examples

Example: Getting Subscription Information

Once your server is registered, you can ask Claude to retrieve subscription information with natural language:

Can you get the subscription information for customer 123e4567-e89b-12d3-a456-426614174000?

Claude will invoke your getCustomerSubscription tool with the appropriate parameters.

Example: Creating a New Subscription

Similarly, you can ask Claude to create a subscription:

Please create a new subscription for customer 123e4567-e89b-12d3-a456-426614174000

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "subscriptionManager" '{"command":"/Users/acmeuser/.local/bin/expose-cli","args":["--url","http://localhost:3000","--timeout","15"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "subscriptionManager": {
            "command": "/Users/acmeuser/.local/bin/expose-cli",
            "args": [
                "--url",
                "http://localhost:3000",
                "--timeout",
                "15"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this to your configuration file:

{
    "mcpServers": {
        "subscriptionManager": {
            "command": "/Users/acmeuser/.local/bin/expose-cli",
            "args": [
                "--url",
                "http://localhost:3000",
                "--timeout",
                "15"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect