JSON RPC 2.0

🚀 MCP-Scala

A server based on the Model Context Protocol (MCP), written in Scala 3.

🚀 Quick Start

Development Phase

This software is currently in the ALPHA version.

• [x] Automatic JSON schema inference
• [x] Define your tools
• [x] Text content section
• [ ] Other content section
• [ ] Notification handling
• [ ] Function handling
• [x] Standard input/output (stdio) transmission
• [ ] HTTP transmission
• [ ] Authorization function

This implementation requires your attention and contributions. Welcome to participate in this project by opening issues or submitting pull requests.

Demo

First, build the server using the following command:

sbt fastLinkJS

Then, use the server in your MCP client:

// Example configuration
{
  "mcpServers": {
    "mcpscala": {
      "disabled": false,
      "timeout": 30,
      "command": "sh",
      "args": ["/path/to/run.sh"],
      "transportType": "stdio"
    }
  }
}

You can run the following tools:

• randomNumber
  • Generate a random number between min and max.
• iota
  • Generate a sequence of numbers from min to max.
• sum
  • Calculate the sum of a set of numbers.

Implement Your Tools

Check the StdioMain.scala file for detailed information.

package dev.capslock.mcpscala

import cats.effect.IO
import cats.effect.IOApp
import dev.capslock.mcpscala.transport.StdioServer
import dev.capslock.mcpscala.mcp.ContentPart
import sttp.tapir.Schema.annotations.description

case class RandomNumberInput(
    @description("Minimum value (inclusive)") min: Int,
    @description("Maximum value (exclusive)") max: Int
) derives io.circe.Decoder,
      sttp.tapir.Schema

def randomNumber(input: RandomNumberInput): IO[Seq[ContentPart]] = IO {
  val random = scala.util.Random.between(input.min, input.max)
  Seq(ContentPart.TextContentPart(random.toString))
}

/** The main entry point for the standard input/output server.
  */
object StdioMain extends IOApp.Simple {
  val tools = Map(
    "randomNumber" -> server.Tool(randomNumber),
  )

  def run: IO[Unit] = {
    StdioServer.serve(Handler.methodHandlers(tools))
  }
}