mcp_on_ruby

Provides a Ruby/Rails integration that exposes a Rails app as a Model Context Protocol (MCP) server, letting you publish application tools (callable functions with JSON Schema input validation) and resources (URI-templated data exposure) over an HTTP/JSON-RPC style transport, with configurable authentication, rate limiting, and security protections.

Evaluated Mar 30, 2026 (21d ago)

Repo ↗ Ai Ml mcp ruby rails json-schema json-rpc ai-integration tooling resources security

⚙ Agent Friendliness

/ 100

Can an agent use this?

🔒 Security

/ 100

Is it safe for agents?

⚡ Reliability

/ 100

Does it work consistently?

Score Breakdown

⚙ Agent Friendliness

MCP Quality

Documentation

Error Messages

Auth Simplicity

Rate Limits

🔒 Security

TLS Enforcement

Auth Strength

Scope Granularity

Dep. Hygiene

Secret Handling

README claims security features including DNS rebinding protection, CORS controls, and token authentication. It also shows using ENV['MCP_AUTH_TOKEN'] for the auth token. No concrete details are provided on TLS enforcement guarantees, secure headers, token storage rotation, or dependency vulnerability status.

⚡ Reliability

Uptime/SLA

Version Stability

Breaking Changes

Error Recovery

Best When

You have a Rails application and want to make selected server-side operations/data accessible to MCP-compatible AI clients with built-in validation and access controls.

Avoid When

You need a fully documented, spec-complete MCP transport plus mature real-time (SSE) support; the README suggests SSE is foundational but not fully implemented.

Use Cases

• Expose Rails business logic as MCP tools for AI agents
• Expose Rails data as MCP resources using URI templates
• Create an MCP server inside an existing Rails app
• Add JSON Schema validation for tool inputs
• Protect MCP endpoints with token authentication and origin controls

Not For

• A standalone MCP server not integrated with Rails
• Use-cases requiring an official hosted SaaS pricing model
• Environments needing GraphQL/gRPC interfaces (not indicated)

Interface

REST API

GraphQL

gRPC

MCP Server

Yes ↗

SDK

Webhooks

Authentication

Methods: Token authentication (MCP_AUTH_TOKEN) Per-tool/resource authorize(context) hooks (custom authorization logic)

OAuth: No Scopes: No

Authentication appears to be token-based with configurable enablement; authorization is also implemented via tool/resource authorize(context) methods. No evidence of OAuth, fine-grained scopes, or multi-tenant claims in the provided content.

Pricing

Free tier: No

Requires CC: No

MIT-licensed Ruby gem; no pricing information for a hosted service.

Agent Metadata

Pagination

none

Idempotent

False

Retry Guidance

Not documented

Known Gotchas

⚠ SSE/real-time is described as 'foundation (full implementation coming soon)', so agents should not rely on complete SSE behavior.
⚠ Tool/resource behavior depends on developer-provided authorize(context) logic; incorrect authorization can cause either overexposure or denial of service to the agent.

Alternatives

Build an MCP server directly in a general-purpose Node/Python service (instead of Rails) Use an existing MCP server framework for Ruby/Python/Node with first-class transport tooling Expose functionality via your own REST/GraphQL API and use an adapter layer for MCP

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Scores are editorial opinions as of 2026-03-30.