Tidewave Rails MCP server

Tidewave Rails

Tidewave Rails is an MCP server that provides runtime-level tools for developing Ruby on Rails apps using coding agents.

Your agent will be able to use this MCP server to talk to your running Rails app in development to:

• execute code in the context of the running app (like a Rails console for agents)
• read the app's live logs
• query your development database
• get source locations of classes and methods
• read documentation pinned to the exact gem versions your app depends on

This MCP server is an open-source component of Tidewave, the agentic development environment for Rails and Phoenix.

You can use this project as a standalone MCP server or integrated with the Tidewave product by following the instructions below.

Installation

1. Add the Tidewave gem to your app

You can add Tidewave Rails to your app by running:

bundle add tidewave --group development

or by manually adding the tidewave gem to the development group in your Gemfile:

gem "tidewave", group: :development

2. Add the Tidewave MCP to your agent/editor

Add the Tidewave MCP server to your editor or MCP client configuration as the type "http" (streamable), pointing to the /tidewave/mcp path and port your web application is running at. For example, http://localhost:3000/tidewave/mcp.

We also have specific instructions for:

• Claude Code
• Codex
• Cursor
• Neovim
• OpenCode
• VS Code
• Others

Usage

As with any other MCP server, your agent will call the tools exposed by the Tidewave MCP whenever it sees fit. But you can also prompt it to call them explicitly.

Available MCP tools

project_eval

Evaluates Ruby code in the context of your running application, with access to its runtime, loaded dependencies, and in-memory data, returning the result plus anything printed to standard output. It's like a Rails console for the agent.

Your agent can use it when it would rather run code than assume behavior, grounding its next step in what the running app actually does. For example, calling a method to see what comes back or reproducing a failing code path against live app state to debug it.

executesqlquery

Runs a SQL query against your app's development database and returns the rows to the agent.

Your agent can use it to run any SQL against your development database. For example, ask it to insert some test records to see how a page looks with realistic data. Or, after a create action, the agent can verify whether the record was saved with the expected values.

get_docs

Looks up the documentation for a class, method, or constant, reading from the exact gem versions locked in your app's Gemfile.lock.

Your agent can use it when it's unsure how a class or method works, so the code it generates is grounded in the docs for the exact versions of the gems your app uses, rather than training data that may be stale or a generic docs lookup that can't guarantee it matches the version your app depends on.

getsourcelocation

Returns the file and line where a class, module, or method is defined, across both your app and its dependencies.

Shortened. The full README is on GitHub.