What is Rig Mcp Server

rig-mcp-server is an example implementation of a Model Context Protocol (MCP) server that utilizes Server-Sent Events (SSE) for communication. It allows for the integration of tools and agents for tasks such as number addition.

Use cases

Use cases include creating interactive web applications that require real-time calculations, integrating with machine learning models for dynamic prompting, and developing tools that enhance user interaction through immediate feedback.

How to use

To use rig-mcp-server, clone the repository and run it using ‘cargo run’. In a separate terminal, start the MCP Inspector with ‘npx @modelcontextprotocol/inspector sse http://127.0.0.1:3001/sse’. You can then access the web interface at ‘http://localhost:5173’.

Key features

Key features include setting up a custom MCP server with ServerSseTransport, connecting a MCP client, registering a custom tool (AddTool) for adding two numbers, listing registered tools, and integrating with RIG for LLM prompting.

Where to use

rig-mcp-server can be used in fields that require real-time data communication and processing, such as web applications, data analysis, and interactive tools that utilize machine learning models.

🔍 Rust MCP Server + Inspector Example: SSE Transport with an Add Tool

credit : https://dev.to/joshmo_dev/using-model-context-protocol-with-rig-m7o

This project demonstrates how to set up an MCP (Model Context Protocol) server and client using Server-Sent Events (SSE) for communication. It includes a simple tool that adds two numbers and integrates with the RIG agent for LLM prompting.

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🚀 Getting Started

Clone this repo and run with:

cargo run

In a separate terminal start the MCP Inspector with:

npx @modelcontextprotocol/inspector sse http://127.0.0.1:3001/sse

You’ll see output like:

Starting MCP inspector...
Proxy server listening on port 3000
New SSE connection
Query parameters: { transportType: 'sse', url: 'http://localhost:3001/sse' }
SSE transport: url=http://localhost:3001/sse, headers=
Connected to SSE transport
Connected MCP client to backing server transport
Created web app transport
Set up MCP proxy
🔍 MCP Inspector is up and running at http://localhost:5173 🚀

You can now view the web interface at http://localhost:5173

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🛠️ Features

• ✅ Sets up a custom MCP server using ServerSseTransport
• ✅ Connects a MCP client to the server
• ✅ Registers a custom tool: AddTool, which adds two numbers
• ✅ Lists registered tools via MCP
• ✅ Integrates with RIG and prompts an LLM agent using the tool

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🧠 Code Overview

#[tool(
    name = "Add",
    description = "Adds two numbers together.",
    params(a = "The first number to add", b = "The second number to add")
)]
async fn add_tool(a: f64, b: f64) -> Result<ToolResponseContent> {
    Ok(tool_text_content!((a + b).to_string()))
}

This defines the Add tool that is registered in the MCP server.

The main function sets up:

• Tracing
• The MCP server and transport (SSE)
• A MCP client that initializes and lists available tools
• A RIG agent with OpenAI backend, which uses the MCP tool

The agent then runs a prompt:

let response = agent.prompt("Add 10 + 10").await;

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🧪 Sample Output

When run successfully, you’ll see logs like:

Initialized: Ok(...)
Tools: Ok([...])
Building RIG agent
Prompting RIG agent
Agent response: Some("20")

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🧰 Tech Stack

• 🦀 Rust with tokio
• 📡 SSE transport from mcp_core
• 🔧 MCP server/client architecture
• 🤖 RIG agent with OpenAI model
• 🌐 MCP Inspector web interface

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📦 Dependencies

Make sure you have these in your Cargo.toml:

[dependencies]
tokio = { version = "1", features = ["full"] }
anyhow = "1"
serde_json = "1"
mcp_core = "..."
mcp_core_macros = "..."
rig = "..."

Replace ... with the appropriate versions based on your environment.

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📍 Inspector GUI

Visit http://localhost:5173 to view and interact with the MCP Inspector UI.

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✅ Test Log Sample

Query parameters: { transportType: 'sse', url: 'http://localhost:3001/sse' }
Connected to SSE transport
Connected MCP client to backing server transport
Set up MCP proxy
Received message for sessionId cdd4a8be-57e2-44e3-9b81-3df300e86f22

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📬 Questions or Feedback?

Feel free to open an issue or start a discussion!