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/posthog-foss --skill exploring-mcp-tool-usagegit clone --depth 1 https://github.com/PostHog/posthog-fossWrote 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/posthog-foss/exploring-mcp-tool-usage)<a href="https://agentmods.dev/skills/posthog/posthog-foss/exploring-mcp-tool-usage"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/exploring-mcp-tool-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/posthog-foss/exploring-mcp-tool-usage"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/exploring-mcp-tool-usage.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Prompt Injection · line 31 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
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 | $0.00111 | $0.01724 |
| Opus 5 | $0.00056 | $0.00862 |
| Sonnet 5 | $0.00022 | $0.00345 |
| Haiku 4.5 | $0.00011 | $0.00172 |
Grade A, and why
exploring-mcp-tool-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 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- exploring-mcp-tool-usage — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Exploring MCP tool usage
Any MCP server instrumented with the @posthog/mcp SDK emits a $mcp_tool_call
event every time an agent invokes a tool. This skill is the front door for a
user who knows they want to look at their MCP tool usage but hasn't picked a
specific question. Offer the menu below, then route to the tool — or the focused
skill — that answers what they choose.
Governed metric first
When the question asks for an MCP failure rate or percentage, call posthog:metric-list before any typed tool or SQL recipe and look for mcp_tool_call_fail_pct. Run an approved, non-drifted match with posthog:data-catalog-metric-run for the canonical headline. If the user also asks which tool or harness drives failures, answer the headline first, then use the per-tool workflows below for a noncanonical breakdown. If no governed metric matches, say so and label the derived rate noncanonical.
Every per-tool tool here is gated behind the mcp-analytics flag, takes a
toolName (the effective tool name — resolved server-side, so pass the name the
agent actually invokes — except posthog:query-mcp-tool-failures, which
matches $exception events and so takes the raw registered $mcp_tool_name)
plus a dateRange, and runs the same query runner the tool-detail UI uses. So
results match the UI, and you never hand-write the HogQL.
Suggested questions
Lead with these when the user is unsure what to ask:
| Ask the user… | Answered by |
|---|---|
| "Which tools fail most, or are slowest?" | exploring-mcp-tool-quality (ranks all tools), then posthog:query-mcp-tool-stats to drill in |
| "How is tool X doing overall?" | posthog:query-mcp-tool-stats — calls, errors, p50/p95, users, sessions, intents |
| "How has tool X trended?" | posthog:query-mcp-tool-daily-stats — day-by-day series |
| "Why is tool X failing?" | posthog:query-mcp-tool-failures — top error messages, by harness (raw tool name) |
| "Who uses tool X the most?" | posthog:query-mcp-tool-top-users — top callers (incl. person email/name) |
| "What gets called right before/after tool X?" | posthog:query-mcp-tool-neighbors (neighborDirection: before/after) |
| "What are agents trying to do with tool X?" | posthog:query-mcp-tool-sample-intents — recent agent intents |
| "What description is tool X registered with?" | posthog:query-mcp-tool-descriptions — distinct descriptions seen |
| "Which harnesses use my MCP, how reliably?" | posthog:query-mcp-harness-breakdown — calls/errors/sessions per client |
| "What are agents trying to do, across all tools?" | exploring-mcp-intent-clusters — semantic goal clusters |
| "Who is connecting, and how active are they?" | posthog:mcp-analytics-sessions-list — one row per session, with client and person |
| "What did this one session do?" | exploring-mcp-sessions — a single agent run's tool sequence |
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 Changed · +4 lines 25cb140b3f37
- 9d ago First seen · 107 lines · 111 tokens per session scan A b917cff4a29d
exploring-mcp-tool-usage is a skill published in the GitHub repository PostHog/posthog-foss (715 stars, last pushed today), licensed MIT. It adds 111 tokens to every session and 1,724 once invoked, about $0.0006 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 2026-09-03.
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