MCP Perl SDK

Model Context Protocol support for Perl and the
Mojolicious real-time web framework.

Features

Please be aware that this module is still in development and will be changing rapidly. Additionally the MCP
specification is getting regular updates which we will implement. Breaking changes are very likely.

• Tool calling, prompts and resources
• Streamable HTTP and Stdio transports
• Scalable with pre-forking web server and async tools using promises
• HTTP client for testing
• Can be embedded in Mojolicious web apps

Installation

All you need is Perl 5.20 or newer. Just install from CPAN.

$ cpanm -n MCP

We recommend the use of a Perlbrew environment.

Streamable HTTP Transport

Use the to_action method to add an MCP endpoint to any Mojolicious application.

use Mojolicious::Lite -signatures;

use MCP::Server;

my $server = MCP::Server->new;
$server->tool(
  name         => 'echo',
  description  => 'Echo the input text',
  input_schema => {type => 'object', properties => {msg => {type => 'string'}}, required => ['msg']},
  code         => sub ($tool, $args) {
    return "Echo: $args->{msg}";
  }
);

any '/mcp' => $server->to_action;

app->start;

Authentication can be added by the web application, just like for any other route.

Server-to-Client Streaming

The HTTP transport can optionally accept GET requests to open a long-lived SSE stream the server can push
notifications to, and DELETE requests to terminate a session. This requires per-process state and is not
compatible with pre-forking web servers, so it is opt-in.

use Mojolicious::Lite -signatures;

use MCP::Server;

my $server = MCP::Server->new;
$server->tool(
  name         => 'echo',
  description  => 'Echo the input text',
  input_schema => {type => 'object', properties => {msg => {type => 'string'}}, required => ['msg']},
  code         => sub ($tool, $args) {
    $tool->notify('notifications/message', {level => 'info', data => "Echoing: $args->{msg}"});
    return "Echo: $args->{msg}";
  }
);

any '/mcp' => $server->to_action({streaming => 1});

app->start;

Stdio Transport

Build local command line applications and use the stdio transport for testing with the to_stdio method.

use Mojo::Base -strict, -signatures;

use MCP::Server;

my $server = MCP::Server->new;
$server->tool(
  name         => 'echo',
  description  => 'Echo the input text',
  input_schema => {type => 'object', properties => {msg => {type => 'string'}}, required => ['msg']},
  code         => sub ($tool, $args) {
    return "Echo: $args->{msg}";
  }
);

$server->to_stdio;

Just run the script and type requests on the command line.

$ perl examples/echo_stdio.pl
{"jsonrpc":"2.0","id":"1","method":"tools/list"}
{"jsonrpc":"2.0","id":"2","method":"tools/call","params":{"name":"echo","arguments":{"msg":"hello perl"}}}