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 ActiveCampaign/postmark-skills --skill postmark-webhooksgit clone --depth 1 https://github.com/ActiveCampaign/postmark-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/activecampaign/postmark-skills/postmark-webhooks)<a href="https://agentmods.dev/skills/activecampaign/postmark-skills/postmark-webhooks"><img src="https://agentmods.dev/badge/skills/activecampaign/postmark-skills/postmark-webhooks/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/activecampaign/postmark-skills/postmark-webhooks"><img src="https://agentmods.dev/badge/skills/activecampaign/postmark-skills/postmark-webhooks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to high
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 →
- high Anti-Refusal · line 174 Skill instructs the agent to never refuse or to always comply. Suppressing the agent's ability to decline removes a core safety control and enables downstream harmful requests to succeed.Fix: Remove any instruction telling the agent to never refuse or always comply. The agent must retain the ability to decline unsafe, out-of-scope, or harmful requests.
- medium Data Exfiltration · line 74 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
- medium Data Exfiltration · line 77 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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 | $0.00054 | $0.03636 |
| Opus 5.5 | $0.00022 | $0.01454 |
| Sonnet 5.5 | $0.00011 | $0.00727 |
| Haiku 4.5 | $0.00005 | $0.00364 |
Grade A, and why
postmark-webhooks scanned grade A with 1 finding 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 1mo 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl "https://api.postmarkapp.com/webhooks" \ How it starts
The opening of the file, as written. The whole thing — 288 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Postmark Webhooks
Overview
Postmark webhooks deliver real-time event data to your endpoint via HTTP POST. Use webhooks to track what happens after you send an email.
This skill covers outbound webhooks — the six event types below. Inbound email webhooks run on separate infrastructure with different retry behavior; see postmark-inbound for those.
| Event | Trigger | Common Use |
|---|---|---|
| Delivery | Email accepted by recipient server | Confirm delivery, update status |
| Bounce | Email rejected by recipient server | Clean lists, alert support |
| SpamComplaint | Recipient marked as spam | Remove from lists, investigate |
| Open | Recipient opened email (tracking pixel) | Engagement analytics |
| Click | Recipient clicked a tracked link | Engagement analytics, conversion tracking |
| SubscriptionChange | Recipient unsubscribed | Update preferences, comply with regulations |
Quick Start
- Create a webhook via API or Postmark dashboard (Server → Webhooks)
- Set your endpoint URL — must accept HTTP POST and return 200
- Select event triggers — choose which events to receive
- Pass verification — Postmark tests your endpoint for every enabled event type on create and edit; each must return HTTP 200 before the webhook is saved as verified
- Handle payloads — parse the JSON body for each event type
- Respond with 200 — acknowledge receipt immediately, then process
Webhook API
Endpoints
| Endpoint | Method | Description |
|---|---|---|
/webhooks |
GET |
List all webhooks for a message stream |
/webhooks/{webhookid} |
GET |
Get a specific webhook |
/webhooks |
POST |
Create a webhook |
/webhooks/{webhookid} |
PUT |
Update a webhook |
/webhooks/{webhookid} |
DELETE |
Delete a webhook |
/webhooks/{Id}/verify |
POST |
Run endpoint verification on demand |
/webhooks/{Id}/statistics |
GET |
Delivery statistics for one webhook (rolling 24 hours) |
What ships with it
5 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.
- 1mo ago Changed · +105 lines · +12 tokens per session fcc4e90369c2
- 1mo ago First seen · 183 lines · 42 tokens per session scan A 12e8eb22ba41
postmark-webhooks is a skill published in the GitHub repository ActiveCampaign/postmark-skills (46 stars, last pushed 1mo ago), licensed MIT. It adds 54 tokens to every session and 3,636 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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