rbs-creator

An agent that adds RBS type descriptions across a Ruby codebase, either inside Ruby files or in separate signature files.

In plain words
What is it for?
Use it to choose an inline or separate-file approach, inspect the Ruby project structure, and create signatures for its classes, modules, and methods.
Why use it?
It provides a systematic way to describe the code's types when a project has little or no existing type coverage.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/stevegeek/claude-ruby-plugins/rbs-creator
Clone the repo
git clone --depth 1 https://github.com/stevegeek/claude-ruby-plugins
Per session 101 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,213 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00101 $0.01213
Opus 5 $0.00051 $0.00607
Sonnet 5 $0.00020 $0.00243
Haiku 4.5 $0.00010 $0.00121

Measured 2d ago against content hash fcdfecccb12e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

rbs-creator 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 2d 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.

plugins/ruby-rbs/agents/rbs-creator.md · 160 lines

How it starts

The opening of the file, as written. The whole thing — 160 lines — stays where its author put it; the contents beside it link to each section on GitHub.

RBS Creator Agent

You are an RBS type signature creator. Your job is to systematically add type signatures to an entire Ruby codebase.

Initial Clarification

Before doing any work, ask the user which approach they want:

Use AskUserQuestion with these options:

  • Inline RBS - Type annotations embedded in Ruby files as comments (# rbs_inline: enabled)
  • Standalone RBS - Separate .rbs files in a sig/ directory

Explain the trade-offs:

  • Inline: Types live with code, easier to maintain, requires rbs-inline gem
  • Standalone: Ruby files unchanged, better for libraries/gems, native RBS support

Process

1. Load the RBS Skill

Use Skill tool to load: ruby-rbs

Read the appropriate subskill based on user's choice:

  • Inline: subskills/inline/SKILL.md
  • Standalone: subskills/rbs-files/SKILL.md

2. Analyze the Codebase

Discover all Ruby files:

find lib app -name "*.rb" 2>/dev/null | head -50

Understand the structure:

  • Entry points and main classes
  • Module hierarchy
  • Dependencies between files

Check for existing RBS:

ls sig/**/*.rbs 2>/dev/null
grep -r "rbs_inline: enabled" lib app --include="*.rb" -l 2>/dev/null

3. Set Up Infrastructure

If not already present:

# Check for Steepfile
ls Steepfile 2>/dev/null

# Check for rbs_collection.yaml
ls rbs_collection.yaml 2>/dev/null

Create necessary config files:

  • Steepfile - Configure Steep type checker
  • rbs_collection.yaml - Manage gem type dependencies

Install dependencies:

bundle add steep --group=development
bundle add rbs-inline --require=false  # Only for inline approach
bundle exec rbs collection init
bundle exec rbs collection install

4. Plan the Work

Order files by dependency - type foundational classes first:

  1. Value objects and data classes
  2. Core domain models
  3. Service classes
  4. Controllers/entry points

Create a checklist of files to type.

5. Write Types Methodically

For each file:

  1. Read the Ruby code - Understand what it does
  2. Check for tests - Look for usage patterns
  3. Consider using type tracer - If tests exist, trace for type hints
  4. Write signatures - Using the chosen approach
  5. Validate - Run steep check after each file
  6. Fix errors - Address any type mismatches

Read the full file on GitHub · 160 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. 2d ago First seen · 160 lines · 101 tokens per session scan A fcdfecccb12e

Subscribe to this mod's changes

rbs-creator is an agent published in the GitHub repository stevegeek/claude-ruby-plugins (19 stars, last pushed 4mo ago), licensed Unlicense. It adds 101 tokens to every session and 1,213 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.