Ruby SDK MCP Server
Build MCP-compliant servers and clients using native Ruby programming patterns.
Data last scanned yesterday · Reviewed today
Overview
The Ruby SDK provides a comprehensive framework for creating Model Context Protocol servers and clients. It handles the complexities of JSON-RPC 2.0 message exchanges, allowing developers to manage tool registration, prompt execution, and resource retrieval within their Ruby applications. The library supports advanced protocol features, including stdio and Streamable HTTP transports, capability negotiation, and server-to-client communication such as sampling and filesystem roots. It simplifies the implementation of the MCP specification through the MCP::Server class, providing hooks for managing the full lifecycle of protocol requests and responses.
Our verdict
This library carries a high risk level with a security score of 48/100. The primary concerns stem from its status as a community-maintained project that has not yet undergone editorial review or security auditing regarding its OAuth and read-only mode implementations. While it features a clean supply chain with zero direct dependencies, potential users should exercise caution until further verification of its authentication and data-handling mechanisms is performed.
- Zero direct dependencies minimize the software supply-chain surface area.
- Comprehensive implementation of the JSON-RPC 2.0 message handling specification.
- Supports both stdio and Streamable HTTP (SSE) transport protocols.
- High level of activity with a commit recorded two days ago.
- Security score of 48/100 indicates significant unreviewed risk areas.
- Community-maintained status lacks formal oversight from the official vendor.
- Critical features like OAuth and read-only modes remain unreviewed.
- License status is marked as NOASSERTION.
Tools
| Tool | Description | Risk |
|---|---|---|
| update_resource | Update a resource and notify the client if subscribed. | medium |
| SummarizeTool | Summarize text using LLM | low |
| LongRunningTool | A tool that supports cancellation | low |
| HealthCheckTool | Verifies the client is still responsive | low |
| collect_info | Collect user info | medium |
| collect_contact | Collect contact info | medium |
| configure_deploy | Configure a deployment | medium |
| authorize_github | Authorize GitHub | medium |
| access_github | Access GitHub | medium |
| new_tool | — | medium |
Compatibility
| Client | Local | Docker | Remote | Read-only |
|---|---|---|---|---|
| Claude Desktop | ||||
| Cursor | ||||
| VS Code | ||||
| Windsurf | ||||
| ChatGPT |
Frequently asked questions
›What transport modes does the Ruby SDK support?
The SDK supports both stdio transport for local applications and Streamable HTTP transport, including Server-Sent Events (SSE).
›What are the deployment requirements for Streamable HTTP transport?
Because the transport stores session and SSE stream state in memory, it must run in a single-process server like Puma with zero workers. If running behind a load balancer, you must enable sticky sessions to ensure requests with the same Mcp-Session-Id reach the same instance.
›How can I prevent memory growth issues when using stdio transport?
You can configure the max_line_bytes keyword in StdioTransport.new to cap the byte length of request frames, which defaults to 4 MiB.
›Are there security restrictions for the Streamable HTTP transport?
Yes, it validates Host and Origin headers by default to prevent DNS rebinding, and it will reject unauthorized values with an HTTP 403 error.
›Is it possible to run the Streamable HTTP transport in a multi-process environment?
Yes, but you must enable stateless mode by setting stateless: true, as this disables the in-memory session management that requires a single process.
Changelog
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