SSH Rails Runner

MCP Server: SSH Rails Runner

An MCP server that enables secure remote execution of Rails console commands via SSH. This server provides tools for both read-only operations and carefully managed mutations in a deployed Rails environment.

This works great with Cursor. You can use Cursor Composer to pull in your Rails model files as context and then use the `execute_read_only`, `dry_run_mutate`, and `execute_mutate` tools to make changes to the database. No need to trudge through complicated Admin UI's to get your data wrangling and analysis done.

Example

![Example](./assets/example.png)

Features

Remote Rails console execution over SSH

Safe read-only operations

Dry-run capability for mutations

Execution of approved mutations

Resource management for code snippets

Installation

Configuration

Set the following environment variables:

Usage with Claude Desktop

Add to your Claude Desktop configuration:

If `CODE_SNIPPET_FILE_DIRECTORY` is not provided, snippets will be stored in a temporary directory (e.g., `/tmp/mcp-ssh-rails-runner-code-snippets`). `PROJECT_NAME_AS_CONTEXT` is optional and helps identify the project context in tool descriptions.

Available Tools

The server now uses a Prepare -> Execute workflow:

`mcp_ssh_rails_runner_prepare_code_snippet`

**Arguments**: `name` (string, for filename), `type` (enum: "readOnly" | "mutate"), `code` (string, Ruby code), `description` (string, optional).

**Function**: Saves the provided Ruby code to a local file named `code_snippet_<name>.json`, marks it as read-only or mutate, and opens the file for review.

**Returns**: The `file://` URI of the created snippet.

`mcp_ssh_rails_runner_execute_code_snippet_read_only`

**Arguments**: `uri` (string, `file://` URI from `prepareCodeSnippet`).

**Function**: Reads the code snippet from the URI, verifies it's marked as `readOnly`, performs a safety check on the code, and executes it.

**Returns**: The output of the Rails command.

`mcp_ssh_rails_runner_execute_code_snippet_mutate`

**Arguments**: `uri` (string, `file://` URI from `prepareCodeSnippet`).

**Function**: **DANGER ZONE!** Reads the code snippet, verifies it's marked as `mutate`, and **executes it directly**. There is no dry run or further safety check within this tool.

**Returns**: The output of the Rails command.

**Usage**: **ONLY CALL THIS AFTER THE USER HAS REVIEWED the prepared code (via the opened file from `prepareCodeSnippet`) AND EXPLICITLY CONFIRMED they want to execute the mutation.**

Security Considerations

Only use with trusted SSH endpoints from your own local machine that is (temporarily) provided access to the remote environment.

**Crucially, always review the code saved by `prepareCodeSnippet` before executing any mutation with `executeCodeSnippetMutate`.** The responsibility for confirming mutations lies with the user and the calling AI.

License

MIT