Sales & CRM·v2.9.0

HubSpot Webhook Handlers Agent Skill

Build and harden HubSpot v3 webhook handlers that survive production: HMAC-SHA256 signature verification, Redis SET NX deduplication…

Context cost
13.2k tokensestimated from the bundle, loaded when it triggers
Bundle
3 files · 52.8 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—v2.9.0
Servers it uses
Noneruns standalone

What it does

Build and harden HubSpot v3 webhook handlers that survive production: HMAC-SHA256 signature verification, Redis SET NX deduplication, async batch processing with immediate 200 ACK, dead-letter queuing for permanent failures, and event-ordering guards for property-change streams. Use when implementing HubSpot webhooks for the first time, hardening an existing handler against retry storms or duplicate processing, debugging signature verification failures, or designing a reliable event pipeline for contact, company, or deal change events.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

event-drivenhubspotintegration-engineeringmarketingwebhookwebhooks
Filed under

Sales & CRM

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md21.4 kB · preview
--- name: hubspot-webhook-handlers allowed-tools: Read, Write, Edit, Bash(curl:*), Bash(jq:*), Bash(python3:*), Grep version: 2.9.0 license: MIT author: Jeremy Longshore <jeremy@intentsolutions.io> compatibility: Designed for Claude Code tags: - hubspot - webhooks - event-driven - integration-engineering ---
26# HubSpot Webhook Handlers
27
28## Overview
29
30Receive and process HubSpot webhook events reliably at production scale. This is not a walkthrough for getting your first event — it is the handler code your integration runs when HubSpot delivers 100 events in a single payload at 2am, when a misconfigured proxy silently strips your signature header, when a 3-day outage causes events to arrive in a burst after recovery, and when a rapid sequence of property updates arrives reversed because HubSpot sends in delivery order rather than chronological order.
31
32The six production failures this skill prevents:
33
341. **Signature verification bypass** — skipping or misconfiguring the HMAC-SHA256 check on X-HubSpot-Signature-v3 allows any party to send spoofed webhook payloads to your endpoint. One misconfigured load balancer or proxy that strips the X-HubSpot-Signature-v3 header silently disables all security — your handler returns 200 to unauthenticated requests without knowing it.
352. **Duplicate delivery** — HubSpot retries unacknowledged webhooks (non-200 response or timeout) for up to 3 days with exponential backoff. If your handler crashes after processing but before responding, the same contact-update event creates duplicate CRM mutations downstream. Redis SET NX on the event ID is the reliable guard.
363. **No replay API — events are permanently lost after the 3-day retry window** — if your handler is down for more than 3 days, HubSpot drops those events permanently. There is no replay endpoint. Dead-letter queues and recovery runbooks are your only mitigation.
374. **Batch event explosion** — a single webhook delivery contains up to 100 events. Synchronous processing of all 100 within the HTTP request context times out (HubSpot timeout: 5 seconds) and returns 5xx, which triggers a retry storm. The correct pattern is to ACK immediately with 200, enqueue the batch, and process asynchronously.
385. **Property change ordering** — HubSpot sends contact.propertyChange events in delivery order, not chronological order. A fast property update followed by a slow one can arrive reversed: your handler sees the newer value first, then overwrites it with the older value. Sequence guards on occurredAt are required.
396. **List-membership scope mismatch** — subscribing to contact.propertyChange for lifecyclestage does not automatically deliver list-membership changes. Those require a separate subscription to the list-membership event type and a separate oauth scope or crm.lists.read scope on the app.
40
41## Prerequisites
42
43- Node.js 18+ (TypeScript examples) or Python 3.10+
44- Express 4.x (or any HTTP server that can expose a raw body buffer for HMAC verification)
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md2,635 words
Files3
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈290
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
12,910
on trigger
The instruction body and 2 supporting files, read only when the skill fires.
6.6%
of a 200k window
Ten skills this size would take about 66% of the window before you open a file.
050k100k150k200k context window

13.2k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

It asks the agent to write files, using whatever file access your client already has. Whether it reaches the network is not declared.

What it asks for
Writes filesyes
Network accessnot declared

Read from the allowed-tools line of this skill’s own SKILL.md. It also asks for Bash, which could do either, so what is not named there is not ruled out. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

3 files, 52.8 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md21.4 kB
  • references/API_REFERENCE.md10.0 kB
  • references/implementation-guide.md21.4 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 3 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# HubSpot Webhook Handlers · 13.2k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/hubspot-webhook-handlers/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/hubspot-webhook-handlers" ] && { [ ! -e .claude/skills/hubspot-webhook-handlers ] || { mv .claude/skills/hubspot-webhook-handlers "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/hubspot-webhook-handlers" .claude/skills/ && echo "Installed .claude/skills/hubspot-webhook-handlers"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add jeremylongshore/hubspot-webhook-handlers

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/hubspot-webhook-handlers/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/hubspot-webhook-handlers/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/hubspot-webhook-handlers" ] && { [ ! -e ~/.claude/skills/hubspot-webhook-handlers ] || { mv ~/.claude/skills/hubspot-webhook-handlers "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/hubspot-webhook-handlers" ~/.claude/skills/ && echo "Installed ~/.claude/skills/hubspot-webhook-handlers" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/hubspot-webhook-handlers/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Version2.9.0
Publishedno release date on file
PriceFree
Referencejeremylongshore/hubspot-webhook-handlers

Versions

v2.9.0 is what is on the shelf; no release here carries a date. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v2.9.0
  • No earlier releases have been published to the marketplace.
Pinning

The install command always fetches the release that is current the day you run it — v2.9.0 today — and cannot ask for an earlier one. The copy on your disk does not change until you run it again.

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