Tidewave Rails

What it is

A gem added to a Rails app's development group. It runs inside the running application and serves MCP over HTTP at /tidewave/mcp on the port your app already uses, so the agent talks to the booted app rather than to a copy of its source.

What you get

• Ruby evaluated in the context of the running application, with its loaded dependencies and in-memory data — the result plus anything printed, like a Rails console the agent can use
• SQL run against the development database, so the agent can seed realistic records or check that a create action saved what it should have
• The server log read back, which is where the params, the backtrace and what actually happened after a request are
• Documentation for a class, method or constant, read from the exact gem versions pinned in Gemfile.lock rather than from training data
• The file and line where something is defined, across the app and its gems — resolved from the running app, so a method generated at runtime is found where grep would miss it

Requirements

A Rails app you can add the gem to as a development-group dependency, and a client that speaks streamable HTTP — point it at http://localhost:3000/tidewave/mcp, or whichever port the app runs on. It raises rather than boot in any environment where code reloading is disabled, which normally includes production, and accepts requests from localhost only unless allow_remote_access is turned on. There are deliberately no tools for listing routes or associations: the author's position is that an agent reading those source files gets more context and can edit them in the same pass.

Setup effort

One command — bundle add tidewave --group development

Tools you get

5 tools named in the project's documentation.