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/posthog-foss/monitoring-capture-servicenpx skills add PostHog/posthog-foss --skill monitoring-capture-servicegit clone --depth 1 https://github.com/PostHog/posthog-fossWhat 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 | $0.00066 | $0.04546 |
| Opus 5 | $0.00033 | $0.02273 |
| Sonnet 5 | $0.00013 | $0.00909 |
| Haiku 4.5 | $0.00007 | $0.00455 |
Grade A, and why
monitoring-capture-service 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 today.
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.
How it starts
The opening of the file, as written. The whole thing — 305 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Monitoring the capture service with Grafana MCP
The capture service (rust/capture/) is PostHog's Rust HTTP ingestion endpoint.
It receives events from SDKs, applies quota/rate limits, and produces to Kafka.
Five deployments run the same binary with different CAPTURE_MODE configs, each in its own K8s namespace.
This skill teaches how to discover live metrics using the Grafana MCP tools rather than memorizing metric names that change as the code evolves.
Environment context
The Grafana MCP is connected to a single Grafana instance scoped to one environment. If the user hasn't specified, ask which environment they want to investigate:
- prod-us — US production (us-east-1)
- prod-eu — EU production (eu-central-1)
Most capture app metrics (e.g. capture_*, http_requests_*, envoy_cluster_*) are
environment-specific by virtue of which Grafana you're connected to — they don't carry
an environment label. MSK and CloudWatch metrics do carry environment labels but
are still scoped to the connected Grafana's AWS account.
Cross-environment comparison requires switching Grafana instances (not possible in one session).
Observability landscape
Capture spans seven telemetry domains. Each has a Grafana datasource and a discovery entry point.
| Domain | Datasource UID | Discovery tool | Scope filter |
|---|---|---|---|
| App metrics (VictoriaMetrics) | victoriametrics |
list_prometheus_metric_names |
regex: "capture_.*" |
| App metrics (realtime) | victoriametrics-realtime |
same | same (lower retention, higher resolution) |
| Logs | P44D702D3E93867EC (Loki-logs) |
list_loki_label_names |
app=~"capture.*" |
| Profiling | pyroscope |
list_pyroscope_profile_types |
service_name="capture-analytics/capture-analytics" |
| Dashboards | n/a | search_dashboards |
query "capture" or "ingestion" |
| CloudWatch (ElastiCache, MSK) | P034F075C744B399F |
query_prometheus |
environment="prod-us" |
| CloudWatch Root (prod-us only) | PAAE47F430CFD1449 |
same | root account AWS metrics (does NOT exist in prod-eu) |
What ships with it
1 file 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.
- today Changed · +1 lines e6dd3267a4d6
- yesterday First seen · 304 lines · 66 tokens per session scan A d6fb2ba5fc70
monitoring-capture-service is a skill published in the GitHub repository PostHog/posthog-foss (713 stars, last pushed today), licensed MIT. It adds 66 tokens to every session and 4,546 once invoked, about $0.0003 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.
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