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 skills add PostHog/ai-plugin --skill understanding-billing-usagegit clone --depth 1 https://github.com/PostHog/ai-pluginWrote 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/ai-plugin/understanding-billing-usage)<a href="https://agentmods.dev/skills/posthog/ai-plugin/understanding-billing-usage"><img src="https://agentmods.dev/badge/skills/posthog/ai-plugin/understanding-billing-usage/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/posthog/ai-plugin/understanding-billing-usage"><img src="https://agentmods.dev/badge/skills/posthog/ai-plugin/understanding-billing-usage.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00148 | $0.02713 |
| Opus 5.5 | $0.00059 | $0.01085 |
| Sonnet 5.5 | $0.00030 | $0.00543 |
| Haiku 4.5 | $0.00015 | $0.00271 |
Grade A, and why
understanding-billing-usage 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 4d 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.
The source is not reproduced here
No licence file
A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.
What ships with it
2 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.
- 4d ago Changed · +1 lines 7dca25dbdff7
- 7d ago Changed abf1ddcd532d
- 1mo ago Changed · +5 lines 2205179e19f6
- 1mo ago First seen · 246 lines · 148 tokens per session scan A 1d1438893747
understanding-billing-usage is a skill published in the GitHub repository PostHog/ai-plugin (96 stars, last pushed today), with no licence file. It adds 148 tokens to every session and 2,713 once invoked, about $0.0006 per session on Opus 5.5. 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 2026-09-05.
Other skills, from other repositories
motherduck-pricing-roi
Assess MotherDuck costs, plan fit, cost attribution, and ROI from the workload's compute and storage needs.
cost
Deep cost exploration and transparency. Shows real token usage, session costs, campaign spend, burn rates, and model breakdown. Reads Claude Code's native session data for exact numbers. Complements /dashboard with focused cost views.
domscribe
Work with Domscribe — the pixel-to-code bridge. Use when setting up, initializing, or configuring Domscribe for a project, OR when editing or modifying UI components (React, Vue, Next.js, Nuxt), implementing features from captured UI annotations, querying runtime context for source locations, exploring component…
writing-extensions
Guide for authoring a new in-process MCP tool extension for gerrit-mcp-server. Use when a user wants to add new Gerrit tools, port a standalone plugin MCP server into the extension framework, or needs a worked example of the ExtensionContext API.
gerrit-task-query
Use when asked to check, list, or act on tasks for a Gerrit change. Triggers on phrases like "what tasks are blocking", "which tasks are actionable", "check task status", "what do I need to do for this change", "what is blocking this change".
find-dependencies
Find all dependencies of a Gerrit change or set of changes — both explicit Depends-on annotations (parsed by the depends-on plugin) and implicit git-chain parents. Use when asked: what does this change depend on, what is blocking this change, show me the dependency chain, are all dependencies merged, which changes…