ActiveAdminMcp

Status: Experimental / WIP

Minimal MCP (Model Context Protocol) server for Rails apps with ActiveAdmin.

Tested Clients

• Claude Code (Anthropic) - HTTP transport

Installation

Add to your Gemfile:

gem "active_admin_mcp"

Then run:

bundle install
rails generate active_admin_mcp:install

The MCP server is automatically mounted at /mcp.

Usage with Claude Code

claude mcp add --transport http my-app http://localhost:3000/mcp/

Or add to your .mcp.json:

{
  "mcpServers": {
    "my-app": {
      "type": "http",
      "url": "http://localhost:3000/mcp/"
    }
  }
}

Available Tools

Tool	Description
list_resources	List all ActiveAdmin resources with their attributes
query	Query a resource using Ransack syntax

Query Examples

Query users where email contains "example.com"
→ query(resource: "User", q: { email_cont: "example.com" })

Find active posts from last week
→ query(resource: "Post", q: { status_eq: "active", created_at_gt: "2025-12-01" })

Future Ideas

• SSE transport support for streaming
• Authentication (API token, HTTP Basic)
• Configurable resource allowlist
• Write operations (create, update, delete)
• Custom tool definitions per resource
• Rate limiting

License

MIT