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 sentdm/sent-plugin --skill sent-webhook-engineergit clone --depth 1 https://github.com/sentdm/sent-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/sentdm/sent-plugin/sent-webhook-engineer)<a href="https://agentmods.dev/skills/sentdm/sent-plugin/sent-webhook-engineer"><img src="https://agentmods.dev/badge/skills/sentdm/sent-plugin/sent-webhook-engineer/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/sentdm/sent-plugin/sent-webhook-engineer"><img src="https://agentmods.dev/badge/skills/sentdm/sent-plugin/sent-webhook-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk warn
- NVIDIA SkillSpector pass
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 | $0.00097 | $0.01914 |
| Opus 5.5 | $0.00039 | $0.00766 |
| Sonnet 5.5 | $0.00019 | $0.00383 |
| Haiku 4.5 | $0.00010 | $0.00191 |
Grade A, and why
sent-webhook-engineer 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 17d 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.
How it starts
The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Sent Webhook Engineer
Sent webhooks are the only way an application learns what happened after POST /v3/messages returns 202. The 202 proves acceptance, never delivery. Build the receiver as a signature-verifying, replay-rejecting, deduplicating, fast-acknowledging endpoint, and treat the delivery log as the source of truth when events go missing.
Signature verification, exactly
Three headers arrive with every delivery:
| Header | Meaning |
|---|---|
x-webhook-signature |
v1,{base64(hmac_sha256)} |
x-webhook-id |
The webhook endpoint UUID — identical on every delivery |
x-webhook-timestamp |
Unix seconds when Sent signed the request |
Verification procedure, in order:
- Capture the raw request body bytes before any JSON parsing.
- Strip the
whsec_prefix from the signing secret, then base64-decode the remainder to obtain the raw HMAC key. - Build the signed content as
{x-webhook-id}.{x-webhook-timestamp}.{raw_body}. - Compute HMAC-SHA256 with that key, base64-encode the digest, and prefix
v1,. - Compare with a constant-time comparison.
- Reject when
abs(now - timestamp) > 300seconds.
The scheme is Svix-compatible. No Sent SDK ships a verification helper in any language, so this code is always hand-written — use scripts/verify_signature.py as the reference implementation and oracle.
The local utility accepts a signing secret explicitly on standard input with --secret-stdin and makes no network requests. It never reads environment variables or installer credentials. Supply only the secret authorized for the delivery being checked; do not put it in command arguments or chat prompts.
x-webhook-id is not an event id. It identifies the endpoint and repeats forever. Using it as a dedupe key silently collapses every event into one. Read references/webhook-signature-and-dedupe.md for the dedupe keys to derive per event type.
Failure triage order
What ships with it
6 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.
- 17d ago Changed · +2 lines d837e7c142e8
- 1mo ago First seen · 114 lines · 97 tokens per session scan A 1ebb526962bd
sent-webhook-engineer is a skill published in the GitHub repository sentdm/sent-plugin (51 stars, last pushed yesterday), licensed MIT. It adds 97 tokens to every session and 1,914 once invoked, about $0.0004 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 2026-08-30.
Other skills, from other repositories
eddi-data
EDDI Manager's data and plumbing conventions — routing, TanStack Query hooks, ApiClient, i18n propagation, MSW mocks and tests. Load when wiring a screen to real data or adding a route.
waniwani-sdk
MCP distribution SDK: build sales funnels, lead generation, booking flows, insurance quote flows, pricing quote flows, and any multi-step conversational MCP app with @waniwani/sdk. Open source createFlow engine (no API key required) with pluggable state backends (in-memory, Redis, Upstash, Cloudflare KV, DynamoDB, or…
migrate-waniwani-sdk-0.22-to-0.23
Migrate a project from @waniwani/sdk 0.22.x to 0.23.x and auto-apply its breaking change: withWaniwani's captureTelemetry option and the CaptureTelemetryOptions type are removed in favour of captureIntent / CaptureIntentOptions, and every wrapped tool advertises one optional intent string instead of the nested…
scaffold-ai-app
Scaffold a Veryfront app with AI tools, agent definitions, and knowledge base.
trtc
Use for TRTC/Tencent RTC requests to integrate, build, troubleshoot, compare, price, migrate, or query SDK/API/docs. Also trigger when the request omits “TRTC” but concerns audio/video, chat, calls, meetings, live, voice rooms, offline push, or AI. Route by product/platform/intent. Products: Chat/IM/TUIKit…
trtc-conference
A guided workflow for building a TRTC Conference web application step by step. TRTC Conference provides real-time group video and voice communication in a web app.