Net::Async::MCP

Async MCP (Model Context Protocol) client for IO::Async.

Connect to MCP servers from Perl using async/await. Works with in-process Perl servers (via MCP module) and external servers over stdio (Node.js, Python, Go, etc.).

Synopsis

use IO::Async::Loop;
use Net::Async::MCP;
use Future::AsyncAwait;

my $loop = IO::Async::Loop->new;

# In-process: direct MCP::Server calls (fastest)
use MCP::Server;
my $server = MCP::Server->new(name => 'MyServer');
$server->tool(
    name         => 'echo',
    description  => 'Echo text',
    input_schema => {
        type       => 'object',
        properties => { message => { type => 'string' } },
        required   => ['message'],
    },
    code => sub { return "Echo: $_[1]->{message}" },
);

my $mcp = Net::Async::MCP->new(server => $server);
$loop->add($mcp);

# Stdio: spawn external MCP server
my $mcp_stdio = Net::Async::MCP->new(
    command => ['npx', '@anthropic/mcp-server-web-search'],
);
$loop->add($mcp_stdio);

# HTTP: remote MCP server
my $mcp_http = Net::Async::MCP->new(
    url => 'https://example.com/mcp',
);
$loop->add($mcp_http);

# Same API for all transports
async sub main {
    await $mcp->initialize;

    my $tools = await $mcp->list_tools;
    say "Available: ", join(', ', map { $_->{name} } @$tools);

    my $result = await $mcp->call_tool('echo', { message => 'Hello MCP!' });
    say $result->{content}[0]{text};  # "Echo: Hello MCP!"

    await $mcp->shutdown;
}

main()->get;

Transports

| Transport | Constructor | Use case | |-----------|-------------|----------| | InProcess | server => $mcp_server | Perl MCP::Server in same process | | Stdio | command => [...] | External servers (any language) | | HTTP | url => '...' | Remote servers (Streamable HTTP) |

Installation

cpanm Net::Async::MCP

Dependencies

• IO::Async >= 0.78
• Future::AsyncAwait >= 0.66
• JSON::MaybeXS
• MCP >= 0.07 (recommended, required for InProcess transport)
• Net::Async::HTTP (recommended, required for HTTP transport)

See also

• MCP - Perl MCP server SDK by Sebastian Riedel
• Langertha - Perl LLM interface (uses Net::Async::MCP for tool calling)
• MCP Specification