rails-ai-context

Your AI is guessing your Rails app. Every guess costs you time.

The problem

You've seen it. Your AI:

• Writes a migration for a column that already exists - didn't check the schema
• Creates a method that duplicates one in a concern - didn't know it was there
• Uses the wrong association name - user.posts when it's user.articles
• Generates tests that don't match your patterns - factories when you use fixtures, or the reverse
• Adds a gem you already have - or calls an API from one you don't
• Misses before_action filters from parent controllers - then wonders why auth fails
• Invents a method that isn't in your codebase - then you spend 10 minutes finding out

You catch it. You fix it. You re-prompt. It breaks something else.

The real cost of AI coding isn't the tokens - it's the correction loop. Every guess is a round-trip: you catch it, you fix it, you re-prompt, and something adjacent breaks. This gem kills the guessing at its source.

Two commands. Problem gone.

gem "rails-ai-context", group: :development
rails generate rails_ai_context:install

Or standalone - no Gemfile needed

gem install rails-ai-context
cd your-rails-app
rails-ai-context init     # interactive setup
rails-ai-context serve    # start MCP server

Now your AI doesn't guess - it asks your app directly. 38 tools and 5 resource templates that query your schema, models, routes, controllers, views, and conventions on demand. Model introspection uses Prism AST parsing - every result carries a [VERIFIED] or [INFERRED] confidence tag so AI knows what's ground truth and what needs runtime checking.

See the difference

One call returns: definition + source code + every caller grouped by type + tests. Replaces 4-5 sequential file reads.

What stops being wrong

Real scenarios where AI goes sideways - and what it does instead with ground truth:

Run these before and after installing to see what changes in your codebase:

# Schema: does AI know what columns exist?
rails 'ai:tool[schema]' table=users

# Trace: find every caller of a method across the codebase
rails 'ai:tool[search_code]' pattern=your_method match_type=trace

# Model: associations, scopes, callbacks, concerns - all resolved
rails 'ai:tool[model_details]' model=User

# Controllers: action source + inherited filters + strong params in one shot
rails 'ai:tool[controllers]' controller=UsersController action=create

Compare what AI outputs with and without these tools wired in. The difference is measured in corrections avoided, not bytes saved.

Three ways to use it

MCP Server (stdio)

AI calls tools directly via the protocol. Each AI tool gets its own config file - auto-detected on project open.

rails ai:serve

→ rails_search_code(pattern: "publishable?", match_type: "trace")
→ rails_get_schema(table: "users")
→ rails_analyze_feature(feature: "billing")

MCP Server (HTTP)

Mount inside your Rails app - inherits routing, auth, and middleware.

# config/routes.rb
mount RailsAiContext::Engine, at: "/mcp"

Native Rails controller transport. No separate process needed.

CLI

Same 38 tools, no server needed. Works in any terminal, any AI tool.

rails 'ai:tool[search_code]' pattern="publishable?" match_type=trace
rails 'ai:tool[schema]' table=users
rails 'ai:tool[analyze_feature]' feature=billing

Full Guide → - every command, every parameter, every configuration option.

Real-world examples

rails 'ai:tool[schema]' table=users

## Table: users
| Column              | Type    | Null | Default |
|---------------------|---------|------|---------|
| email               | string  | NO   | [unique] |
| subscription_status | string  | yes  | "free"   |
| created_at          | datetime| NO   |          |

AI sees subscription_status already exists. Checks the model, then generates a correct migration - first attempt.

rails 'ai:tool[controllers]' controller=PostsController action=create

# PostsController#create

Filters: before_action :authenticate_user!, before_action :set_post (only: show, edit)
Strong params: post_params → title, body, published_at
Renders: redirect_to @post | render :new

AI sees the inherited authenticate_user! filter, the actual strong params, and the render paths. No guessing.

# Check existing view patterns
rails 'ai:tool[view]' controller=dashboard
# → templates with ivars, Turbo frames, Stimulus controllers, partial locals

# See existing components + usage examples
rails 'ai:tool[component_catalog]' detail=standard
# → ViewComponent/Phlex props, slots, previews, sidecar assets

# Get Stimulus data-attributes
rails 'ai:tool[stimulus]' controller=chart
# → correct HTML with dashes (not underscores) + reverse view lookup

38 Tools

Every tool is read-only and returns data verified against your actual app - not guesses, not training data.