Fast MCP Server
A demo MCP server from https://github.com/modelcontextprotocol/python-sdk guide
What is Fast MCP Server?
Fast MCP Server is a Model Context Protocol (MCP) server that allows AI assistants like Claude, Cursor, and VS Code to demo mcp server from https://github.com/modelcontextprotocol/python-sdk guide
A demo MCP server from https://github.com/modelcontextprotocol/python-sdk guide
This server falls under the Developer Tools category on MCPgee, the world's largest MCP server directory with 33,000+ servers.
Features
- A demo MCP server from https://github.com/modelcontextprotoc
Use Cases
Maintainer
Works with
Installation
Manual Installation
npx fastConfiguration
Configuration Details
claude_desktop_config.json
Performance
Response Metrics
Resource Usage
How to Set Up and Use Fast MCP Server
Fast MCP is a Ruby gem and Rails engine that makes it straightforward to embed a Model Context Protocol server directly into any Rack-based web application — Rails, Sinatra, Hanami, or plain Rack. It lets you expose Ruby classes as MCP tools with full argument validation, share application data as MCP resources with real-time subscription support, and choose from STDIO, HTTP streaming, or SSE transports. Developers use it to give AI assistants structured, authenticated access to application business logic without building a separate microservice.
Prerequisites
- Ruby 3.1 or later installed
- A Rack-based web application (Rails 7+, Sinatra, Hanami, or plain Rack)
- Bundler gem installed
- An MCP-compatible client such as Claude Desktop
Add fast-mcp to your Gemfile
Add the gem to your application's Gemfile and install it. For Rails applications, a generator creates the initializer automatically.
bundle add fast-mcp
# For Rails:
bin/rails generate fast_mcp:installReview the generated initializer
The Rails generator creates config/initializers/fast_mcp.rb with sensible defaults. Review and customize the server name, version, path prefix, authentication settings, and allowed origins.
Define a tool class
Create a Ruby class that inherits from FastMcp::Tool. Declare the tool's description, arguments with types and validation, and implement the call method with your business logic.
class SummarizeTool < FastMcp::Tool
description "Summarize application data"
argument :record_id, Integer, required: true
def call(record_id:)
record = MyModel.find(record_id)
{ summary: record.summary }
end
endRegister tools and resources with the server
In your initializer or application bootstrap, register your tool and resource classes with the Fast MCP server instance.
server = FastMcp::Server.new(name: 'my-app-mcp', version: '1.0.0')
server.register_tool(SummarizeTool)
server.register_resource(StatisticsResource)
server.startConfigure your MCP client to connect
For STDIO transport (recommended for desktop clients), run your Rails app as an MCP command. For HTTP/SSE, point your client at the configured path prefix (default: /mcp).
Fast MCP Server Examples
Client configuration
Configure Claude Desktop to launch your Rails app as an MCP server over STDIO. Replace my-rails-app with your application directory and Gemfile path.
{
"mcpServers": {
"fast-mcp": {
"command": "bundle",
"args": ["exec", "rails", "runner", "FastMcp.start_stdio_server"],
"cwd": "/path/to/your/rails-app"
}
}
}Prompts to try
Example prompts once your application's tools and resources are exposed through Fast MCP.
- "Call the SummarizeTool with record_id 42 and show me the result"
- "List all available MCP tools exposed by this Rails application"
- "Read the StatisticsResource and tell me which metrics are trending up"
- "Use the application's search tool to find all records modified in the last 24 hours"
- "Invoke the ReportTool and format the output as a markdown table"Troubleshooting Fast MCP Server
The Rails generator fails or fast_mcp:install task is not found
Ensure `bundle add fast-mcp` completed successfully and the gem is in your Gemfile.lock. Run `bundle exec rails generate` to list available generators and confirm fast_mcp appears.
MCP client connects but no tools are listed
Verify that you have called server.register_tool() for each tool class and that server.start is called after all registrations. Check your initializer is being loaded by confirming the file exists in config/initializers/.
Authentication errors when connecting from a remote MCP client
Set authenticate: true and auth_token: 'your-secret' in the initializer, then pass the token as a Bearer header from your client. For local desktop clients, localhost_only: true (the default) is usually sufficient.
Frequently Asked Questions about Fast MCP Server
What is Fast MCP Server?
Fast MCP Server is a Model Context Protocol (MCP) server that demo mcp server from https://github.com/modelcontextprotocol/python-sdk guide It connects AI assistants to external tools and data sources through a standardized interface.
How do I install Fast MCP Server?
Follow the installation instructions on the Fast MCP Server GitHub repository. Clone the repo, install dependencies, and add the server config to your AI client.
Which AI clients work with Fast MCP Server?
Fast MCP Server works with all major MCP-compatible AI clients including Claude Desktop, Claude Code, Cursor, VS Code (GitHub Copilot), Windsurf, and Cline.
Is Fast MCP Server free to use?
Yes, Fast MCP Server is open source and available under the MIT license. You can use it freely in both personal and commercial projects.
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Quick Config Preview
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