MCP client

Connect to an MCP server over stdio, inspect its tools and resources, call one directly, and adapt the discovered tools for use in an nimgent agent.

The server executable path is supplied on the command line. After discovery, the example calls a tool named echo, then converts all discovered tools with asToolsAsync so they can be passed to normal nimgent model calls.

import std/[asyncdispatch, json, os, sequtils, strutils]
import nimgent/mcp

proc main() {.async.} =
  if paramCount() != 1:
    quit("usage: mcp_client <path-to-echo-server>")
  let client = await connectMcpStdioAsync(@[paramStr(1)])
  defer: client.close()

  let tools = await client.listToolsAsync()
  echo "discovered: ", tools.mapIt(it.name).join(", ")

  let result = await client.callToolAsync("echo", %*{"text": "hello from nimgent"})
  echo result.content

  let resources = await client.listResourcesAsync()
  echo "resources: ", resources.len

  let adapted = await client.asToolsAsync(prefix = "echo_")
  echo "nimgent tools: ", adapted.mapIt(it.name).join(", ")

waitFor main()

Compile it with the path to an MCP stdio server that exposes an echo tool:

nim c -r examples/mcp_client.nim /path/to/echo-server

View the source example