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rails-ai-bridge: Instructions file for Gemini CLI

GEMINI.md

rails-ai-bridge GEMINI.md is an instructions file for Gemini CLI from igmarin/rails-ai-bridge. It costs 897 tokens per session, scanned A, a copy of rails-ai-bridge AGENTS.md, MIT.

A Ruby library that examines a Ruby on Rails application and gives AI assistants structured information about it through MCP, a standard way for tools to exchange context. It can also write context files for several coding assistants, but does not write to the application's database.

In plain words
What is it for?
Use it to inspect Rails applications, expose their structure and selected data through assistant tools, and produce context files for supported coding assistants.
Why use it?
It helps an assistant understand an existing Rails codebase without manually searching through every model, route, and configuration file. This reduces repeated setup and avoids changing production data during inspection.

Instructions file for Gemini CLI

Written for Gemini CLI: the file is GEMINI.md. Also seen: mentions Codex; mentions Gemini CLI.

This is igmarin/rails-ai-bridge's own configuration. It tells Gemini CLI how to work on rails-ai-bridge itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything rails-ai-bridge configures →

not rated 16repo changed 1mo ago A scan 897 tokens copy · 84% MIT
View source ↗ igmarin/rails-ai-bridge
Reuse

Borrowing it

Nothing to install: this file belongs to igmarin/rails-ai-bridge. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/igmarin/rails-ai-bridge/main/GEMINI.md
Clone the repo
git clone --depth 1 https://github.com/igmarin/rails-ai-bridge

Made for: Gemini CLI.

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Per session 897 This file is loaded in full into every session.
When invoked 897 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 84% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00897 $0.00897
Opus 5.5 $0.00359 $0.00359
Sonnet 5.5 $0.00179 $0.00179
Haiku 4.5 $0.00090 $0.00090

Measured 1mo ago against content hash c283a718d22d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

rails-ai-bridge GEMINI.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

84% identical to rails-ai-bridge AGENTS.md — 56 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

GEMINI.md · 57 lines

How it starts

The opening of the file, as written. The whole thing — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.

GEMINI.md — rails-ai-bridge development guide

Ruby gem that reads a Rails app and gives assistants that map over MCP and committed context files. It does not write to the host database.

Architecture

  • lib/rails_ai_bridge.rb — Main entry point, public API (Zeitwerk autoloaded)
  • lib/rails_ai_bridge/configuration.rb — User-facing config with presets (:standard, :full)
  • lib/rails_ai_bridge/introspector.rb — Orchestrates sub-introspectors
  • lib/rails_ai_bridge/introspectors/ — Built-in introspector classes; :standard preset runs 9, :full runs 27 (see Configuration::PRESETS). Registry: Introspector::BUILTIN_INTROSPECTORS (includes opt-in symbols such as database_stats, non_ar_models not listed in those presets).
  • lib/rails_ai_bridge/tools/ — 22 built-in MCP tools using the official mcp SDK (hosts can add more via additional_tools)
  • lib/rails_ai_bridge/serializers/ — Output formatters (claude, claude_rules, codex, cursor_rules, devin, devin_rules, copilot, copilot_instructions, gemini, rules, markdown, JSON)
  • lib/rails_ai_bridge/resources.rb — MCP resources (static data AI clients read directly)
  • lib/rails_ai_bridge/server.rb — MCP server configuration (stdio + HTTP transports)
  • lib/rails_ai_bridge/middleware.rb — Rack middleware for auto-mounting MCP HTTP endpoint
  • lib/rails_ai_bridge/fingerprinter.rb — SHA256 file fingerprinting for cache invalidation
  • lib/rails_ai_bridge/doctor.rb — Diagnostic checks and AI readiness scoring
  • lib/rails_ai_bridge/watcher.rb — File watcher for auto-regenerating context files
  • lib/rails_ai_bridge/engine.rb — Rails Engine for auto-integration
  • lib/generators/rails_ai_bridge/install/ — Install generator (creates .mcp.json, initializer, context files)

Key Design Decisions

  1. Built on official mcp SDK — not a custom protocol implementation
  2. Zero-config — Railtie auto-registers at boot, introspects without setup
  3. Graceful degradation — works without DB by parsing schema.rb as text
  4. Read-only tools only — all MCP tools are annotated as non-destructive
  5. Dual output — static files (GEMINI.md) + live MCP server (stdio/HTTP)
  6. Diff-aware — context regeneration skips unchanged files
  7. Per-assistant serializers — each AI tool gets tailored output format
  8. Zeitwerk autoloading — files loaded on-demand, not all upfront
  9. Introspector presets — :standard (9 core) default, :full (27 introspectors; optional extras such as database_stats, non_ar_models) for power users
  10. MCP auto-discovery — .mcp.json generated by install generator
  11. Compact by default — context files ≤150 lines, MCP tools use detail parameter (summary/standard/full)
  12. Per-tool split rules — .codex/, .cursor/rules/, .devin/rules/, .github/instructions/

Read the full file on GitHub · 57 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago Changed c283a718d22d
  2. 1mo ago Changed · -1 lines · -20 tokens per session c359bc29d665
  3. 2mo ago First seen · 58 lines · 917 tokens per session scan A 1be77533ae14

Subscribe to this mod's changes

rails-ai-bridge GEMINI.md is an instructions file published in the GitHub repository igmarin/rails-ai-bridge (16 stars, last pushed 13d ago), licensed MIT. It adds 897 tokens to every session, about $0.0036 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 84% identical to rails-ai-bridge AGENTS.md, differing in 56 lines, and is treated as a copy.

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