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.
npx agentmods add skills/posthog/skills/feature-flags-rubynpx skills add PostHog/skills --skill feature-flags-rubygit clone --depth 1 https://github.com/PostHog/skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/posthog/skills/feature-flags-ruby)<a href="https://agentmods.dev/skills/posthog/skills/feature-flags-ruby"><img src="https://agentmods.dev/badge/skills/posthog/skills/feature-flags-ruby.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00014 | $0.00464 |
| Opus 5 | $0.00007 | $0.00232 |
| Sonnet 5 | $0.00003 | $0.00093 |
| Haiku 4.5 | $0.00001 | $0.00046 |
Grade A, and why
feature-flags-ruby 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 3d 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.
This is a copy
80% identical to feature-flags-api — 17 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.
What it actually says
PostHog feature flags for Ruby
This skill helps you add PostHog feature flags to Ruby applications.
Reference files
references/ruby.md- Ruby feature flags installation - docsreferences/adding-feature-flag-code.md- Adding feature flag code - docsreferences/best-practices.md- Feature flag best practices - docs
Consult the documentation for API details and framework-specific patterns.
Key principles
- Environment variables: Always use environment variables for PostHog keys. Never hardcode them.
- Minimal changes: Add feature flag code alongside existing logic. Don't replace or restructure existing code.
- Boolean flags first: Default to boolean flag checks unless the user specifically asks for multivariate flags.
- Server-side when possible: Prefer server-side flag evaluation to avoid UI flicker.
PostHog MCP tools
Check if a PostHog MCP server is connected. If available, look for tools related to feature flag management (creating, listing, updating, deleting flags). Use these tools to manage flags directly in PostHog rather than requiring the user to do it manually in the dashboard.
Framework guidelines
- posthog-ruby is the Ruby SDK gem name (add
gem 'posthog-ruby'to Gemfile) but require it withrequire 'posthog'(NOTrequire 'posthog-ruby') - Use PostHog::Client.new(api_key: key, host: host) for instance-based initialization in scripts and CLIs
- In CLIs and scripts: MUST call client.shutdown before exit or all events are lost
- Use begin/rescue/ensure with shutdown in the ensure block for proper cleanup
- capture and identify take a single hash argument: client.capture(distinct_id: 'user_123', event: 'my_event', properties: { key: 'value' })
- capture_exception takes POSITIONAL args (not keyword): client.capture_exception(exception, distinct_id, additional_properties) — do NOT use
distinct_id:keyword syntax
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 3d ago First seen · 40 lines · 14 tokens per session scan A 4a9df7d6e559
feature-flags-ruby is a skill published in the GitHub repository PostHog/skills (60 stars, last pushed today), licensed MIT. It adds 14 tokens to every session and 464 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 80% identical to feature-flags-api, differing in 17 lines, and is treated as a copy.
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