Ruby

Drop a .rb file.
517 lines. No gems.

zeromcp vs mcp gem — side by side.

Dependencies

0 ZeroMCP

vs.

90 Official SDK

Throughput

3,217 req/s

vs.

2,163 req/s

Memory

26 MB

vs.

56 MB

This is a hello world

Require, server instantiation, class-based registration, schema definition, and transport setup. 12 lines before your tool does anything.

mcp gem 12 lines

require 'mcp'

server = MCP::Server.new(
  name: "test", version: "1.0.0")
server.register_tool("hello",
  description: "Say hello",
  input_schema: {
    name: { type: "string" }
  }) do |args|
  "Hello, #{args['name']}!"
end
server.run_stdio

This is the whole server

No require. No server class. No registration blocks.
Drop it in a folder and run zeromcp serve.

ZeroMCP 8 lines

# tools/hello.rb
TOOL = {
  description: "Say hello",
  input: { name: "string" }
}

def execute(args, ctx)
  "Hello, #{args['name']}!"
end

HTTP Performance — Head to Head

Same hello tool. Same methodology. 5-minute sustained load in Docker. Rack+Puma for ZeroMCP, stdio proxy for the official SDK.

ZeroMCP (Rack+Puma) 3,217 0.06% 26 MB 1.5x

Official SDK 2,163 0.04% 56 MB

ZeroMCP HTTP Frameworks

ZeroMCP embedded natively in Ruby frameworks. No proxy. No subprocess. 30-second sustained load.

Rack+Puma 6,064 0.89ms — 33 MB

Sinatra 3,907 0.84ms — 37 MB

What's different

SandboxEnforced. Not advisory.
CredentialsPer-directory. Not ENV[].
ProcessesOne. Not N.
Hot reloadBuilt-in. Not restart.
ComposabilityConnect remote MCP servers. Official SDK can't.
TransportStreamable HTTP by default. Stdio too.

When to use the official SDK

ZeroMCP makes trade-offs. Here's what you give up.

Resources and prompts

ZeroMCP implements tools only. If you need MCP resources, prompts, or sampling, use the official SDK.

Block DSL

ZeroMCP uses file-based tools. If you prefer the block DSL registration pattern, use the official gem.

Spec parity

The official SDK tracks every spec change immediately. ZeroMCP prioritizes stability over spec completeness.

Enterprise support

The official SDK is maintained by the MCP specification team at Anthropic. ZeroMCP is maintained by the antidrift team (Reloop Labs, LLC).

Drop a .rb file. It's an MCP tool.

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Drop a .rb file.517 lines. No gems.