io.github.crisnahine/rails-ai-context

Official

by crisnahine · Ruby

Rails AI Context

38 MCP tools give AI agents live Rails schema, routes, models, and conventions.

Exposes Rails framework schema, routes, models, and conventions as 38 MCP tools for AI code context.

Topics

aiclaudecopilotcursordeveloper-toolsintrospectionmcpmodel-context-protocolrailsrubyopencoderails-aillmai-codingruby-gemrails-toolscodexcodex-clicopilot-chatcopilot-cli

README.md20 KBView on GitHub

rails-ai-context

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

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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.

bash

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

Or standalone - no Gemfile needed

bash

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

Install demo

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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

Trace demo

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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:

You ask AI to...	Without - AI guesses	With - AI verifies first
Add a `subscription_tier` column to users	Writes the migration, duplicates an existing column	Reads live schema, spots `subscription_status` already exists, asks before migrating
Call `user.posts` in a controller	Uses the guess; runtime `NoMethodError`	Resolves the actual association (`user.articles`) from the model
Write tests for a new model	Scaffolds with FactoryBot	Detects your fixture-based suite and matches it
Fix a failing create action	Misses inherited `before_action :authenticate_user!`	Returns parent-controller filters inline with the action source
Build a dashboard page	Invents Tailwind classes from memory	Returns your actual button/card/alert patterns, copy-paste ready
Trace where `publishable?` is used	Reads 6 files sequentially, still misses callers	Single call: definition + source + every caller + tests

<details> <summary>Verify it on your own app</summary>

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

bash

# 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.

</details>

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.

code

rails ai:serve

code

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

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MCP Server (HTTP)

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

ruby

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

Native Rails controller transport. No separate process needed.

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CLI

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

bash

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

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

Real-world examples

<details> <summary>"Add a subscription field to users"</summary>

bash

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

code

## 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.

</details> <details> <summary>"Fix the broken post creation flow"</summary>

bash

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

code

# 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.

</details> <details> <summary>"Build a new dashboard view"</summary>

bash

# 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

</details>

38 Tools

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

<details open> <summary>Search & Trace</summary>

Tool	What it does
`search_code`	Trace: definition + source + callers + tests. Also: definition, call, class filters
`get_edit_context`	Method-aware code extraction with class context

</details> <details open> <summary>Understand</summary>

Tool	What it does
`analyze_feature`	Full-stack: models + controllers + routes + services + jobs + views + tests
`get_context`	Composite: schema + model + controller + routes + views in one call
`onboard`	Narrative app walkthrough (quick/standard/full)

</details> <details open> <summary>Schema & Models</summary>

Tool	What it does
`get_schema`	Columns with indexed/unique/encrypted/default hints
`get_model_details`	AST-parsed associations, validations, scopes, enums, macros - each result tagged `[VERIFIED]` or `[INFERRED]`
`get_callbacks`	Callbacks in Rails execution order with source
`get_concern`	Concern methods + source + which models include it

</details> <details open> <summary>Controllers & Routes</summary>

Tool	What it does
`get_controllers`	Actions + inherited filters + render map + strong params
`get_routes`	Code-ready helpers (`post_path(@record)`) + required params

</details> <details open> <summary>Views & Frontend</summary>

Tool	What it does
`get_view`	Templates with ivars, Turbo wiring, Stimulus refs, partial locals
`get_stimulus`	HTML data-attributes (dashes!) + targets + values + actions
`get_partial_interface`	What locals to pass + what methods are called on them
`get_turbo_map`	Broadcast → subscription wiring + mismatch warnings
`get_frontend_stack`	React/Vue/Svelte/Angular, Hotwire, TypeScript, package manager

</details> <details open> <summary>Testing & Quality</summary>

Tool	What it does
`get_test_info`	Fixtures + relationships + test template matching your patterns
`generate_test`	Test scaffolding matching your project's patterns
`validate`	Syntax + semantic + Brakeman security in one call
`security_scan`	Brakeman static analysis - SQL injection, XSS, mass assignment
`performance_check`	N+1 risks, missing indexes, counter_cache, eager load candidates

</details> <details open> <summary>App Config & Services</summary>

Tool	What it does
`get_conventions`	Auth checks, flash messages, create action template, test patterns
`get_config`	Database, auth framework, assets, cache, queue, Action Cable
`get_gems`	Notable gems with versions, categories, config file locations
`get_env`	Environment variables + credentials keys (not values)
`get_helper_methods`	App + framework helpers with view cross-references
`get_service_pattern`	Interface, dependencies, side effects, callers
`get_job_pattern`	Queue, retries, guard clauses, broadcasts, schedules
`get_component_catalog`	ViewComponent/Phlex: props, slots, previews, sidecar assets

</details> <details open> <summary>Data & Debugging</summary>

Tool	What it does
`dependency_graph`	Model/service dependency graph in Mermaid or text format
`migration_advisor`	Migration code generation with reversibility + affected models
`search_docs`	Bundled topic index with weighted keyword search
`query`	Safe read-only SQL with timeout, row limit, column redaction
`read_logs`	Reverse file tail with level filtering and sensitive data redaction
`diagnose`	One-call error diagnosis with classification + context + git + logs
`review_changes`	PR/commit review with per-file context + warnings
`runtime_info`	Live DB pool, table sizes, pending migrations, cache stats, queue depth
`session_context`	Session-aware context tracking across tool calls

</details>

All 38 tools with parameters → | Real-world recipes →

Live Resources (VFS)

AI clients can also read structured data through resource templates - rails-ai-context:// URIs that introspect fresh on every request. Zero stale data.

Resource Template	What it returns
`rails-ai-context://controllers/{name}`	Actions, inherited filters, strong params
`rails-ai-context://controllers/{name}/{action}`	Action source code with applicable filters
`rails-ai-context://views/{path}`	View template content (path traversal protected)
`rails-ai-context://routes/{controller}`	Live route map filtered by controller
`rails://models/{name}`	Per-model details: associations, validations, schema

Plus 9 static resources (schema, routes, conventions, gems, controllers, config, tests, migrations, engines) that AI clients read directly.

Anti-Hallucination Protocol

Every generated context file ships with 6 rules that force AI verification before writing code. The protocol targets the exact cognitive failures that produce confident-wrong code: statistical priors overriding observed facts, pattern completion beating verification, stale context lies.

<details> <summary>The 6 rules (shown to AI in every CLAUDE.md / .cursor/rules / .cursorrules / .github/instructions)</summary>

Verify before you write. Never reference a column, association, route, helper, method, class, partial, or gem not verified in THIS project via a tool call in THIS turn. Never invent names that "sound right."
Mark every assumption. If proceeding without verification, prefix with [ASSUMPTION]. Silent assumptions forbidden. "I'd need to check X first" is a preferred answer.
Training data describes average Rails. This app isn't average. When something feels "obviously" standard Rails, query anyway. Check rails_get_conventions + rails_get_gems BEFORE scaffolding.
Check the inheritance chain before every edit. Inherited before_action filters, concerns, includes, STI parents. Inheritance is never flat.
Empty tool output is information, not permission. "0 callers found" signals investigation, not license to proceed on guesses.
Stale context lies. Re-query after writes. Earlier tool output may be wrong after edits.

Enabled by default. Disable with config.anti_hallucination_rules = false if you prefer your own rules.

</details>

How it works

mermaid

graph TD
    A["Your Rails App\nmodels + schema + routes + controllers + views + jobs"] -->|"39 introspectors"| B

    B["rails-ai-context\nPrism AST parsing · Cached · Confidence-tagged\nVFS: rails-ai-context:// URIs introspected fresh"]

    B --> C["MCP Server\nstdio / HTTP\n38 tools · 5 templates"]
    B --> D["CLI Tools\nRake / Thor\nSame 38 tools"]
    B --> E["Static Files\nCLAUDE.md · .cursor/rules/ · .cursorrules\n.github/instructions/"]

    style A fill:#4a9eff,stroke:#2d7ad4,color:#fff
    style B fill:#2d2d2d,stroke:#555,color:#fff
    style C fill:#0984e3,stroke:#0770c2,color:#fff
    style D fill:#00cec9,stroke:#00b5b0,color:#fff
    style E fill:#a29bfe,stroke:#8c83f0,color:#fff

Install

Option A - In Gemfile:

bash

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

Option B - Standalone (no Gemfile entry needed):

bash

gem install rails-ai-context
cd your-rails-app
rails-ai-context init

Both paths ask which AI tools you use (Claude Code, Cursor, GitHub Copilot, OpenCode, Codex CLI) and whether you want MCP or CLI mode. Each tool gets its own MCP config file - auto-detected on project open.

Commands

In-Gemfile	Standalone	What it does
`rails ai:context`	`rails-ai-context context`	Generate context files
`rails 'ai:tool[NAME]'`	`rails-ai-context tool NAME`	Run any of the 38 tools
`rails ai:tool`	`rails-ai-context tool --list`	List all available tools
`rails ai:serve`	`rails-ai-context serve`	Start MCP server (stdio)
`rails ai:doctor`	`rails-ai-context doctor`	Diagnostics + AI readiness score
`rails ai:watch`	`rails-ai-context watch`	Auto-regenerate on file changes

Documentation


Quickstart	5-minute getting started
Tools Reference	All 38 tools with every parameter
Recipes	Real-world workflows and examples
Custom Tools	Build and test your own MCP tools
Configuration	40+ config options with defaults
AI Tool Setup	Claude, Cursor, Copilot, OpenCode, Codex
Architecture	System design and internals
Introspectors	All 39 introspectors and AST engine
Security	4-layer SQL safety and file blocking
CLI Reference	Commands and argument syntax
Standalone	Use without Gemfile entry
Troubleshooting	Common issues and fixes
FAQ	Frequently asked questions

Build your own tools

ruby

# app/mcp_tools/rails_get_business_metrics.rb
class RailsGetBusinessMetrics < MCP::Tool
  tool_name "rails_get_business_metrics"
  description "Key business metrics for this app"

  def call(period: "week")
    MCP::Tool::Response.new([{ type: "text", text: "Users this #{period}: #{User.recent.count}" }])
  end
end

# config/initializers/rails_ai_context.rb
config.custom_tools = [RailsGetBusinessMetrics]

Test with the built-in TestHelper (works with RSpec and Minitest):

ruby

include RailsAiContext::TestHelper

response = execute_tool("business_metrics", period: "month")
assert_tool_response_includes(response, "Users")

Custom Tools Guide →

Configuration

ruby

# config/initializers/rails_ai_context.rb
if defined?(RailsAiContext)
  RailsAiContext.configure do |config|
    config.ai_tools   = %i[claude cursor] # Which AI tools to generate for
    config.tool_mode  = :mcp              # :mcp (default) or :cli
    config.preset     = :full             # :full (39 introspectors) or :standard (17)
  end
end

All 40+ configuration options →

Observability

Every MCP tool call fires an ActiveSupport::Notifications event:

ruby

ActiveSupport::Notifications.subscribe("rails_ai_context.tools.call") do |event|
  Rails.logger.info "[MCP] #{event.payload[:method]} - #{event.duration}ms"
end

Requirements

Ruby >= 3.2 Rails >= 7.1
Optional: brakeman for security scanning, listen for watch mode, ripgrep for fast search

About

Built by a Rails developer with 10+ years of production experience. 2154 tests + 100-example e2e harness. 38 tools. 5 resource templates. 39 introspectors. Standalone or in-Gemfile. MIT licensed. Contributions welcome.

If this gem saves you time, consider sponsoring the project.

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Install

mcpb

mcpb: https://github.com/crisnahine/rails-ai-context/releases/download/v5.12.0/rails-ai-context-mcp.mcpb