You are helping me build the following AI agent workflow.

## Goal
On-Demand Website Screenshot Generator: Accepts a URL via webhook, validates it for security, and returns a screenshot link from ScreenshotMachine.

## Specification
- What it does: Get instant screenshots of any website by sending a URL via webhook, with built-in security checks to block malicious requests. You receive a direct link to the captured image automatically, enabling visual monitoring or asset creation without manual steps.
- Trigger: Triggered by an event (Manual · on webhook request)
- Autonomy: Fully hands-off
- Expected setup effort: under an hour
- Tools/services involved:
  - n8n: Workflow orchestration and automation logic
  - ScreenshotMachine API: Capturing website screenshots via HTTP request

## Known pitfalls, handle each one explicitly in your implementation
1. SSRF vulnerabilities can expose internal services, so strictly validate the domain against a whitelist before making the request.
2. ScreenshotMachine requires valid public URLs, ensure you reject localhost or private IP addresses to avoid silent failures.

## Reference implementation
https://n8n.io/workflows/4594 (workflow template)
Fetch and inspect this before building. If it matches my stack, adapt it;
if not, rebuild the pattern with my tools.

## Process requirements
1. Before building: ask me which of the listed tools I actually use and
   what my platform is (n8n / Make / code / other). Do not assume.
2. Adapt the pattern to my answers; do not force the reference stack.
3. Address every pitfall above; tell me how you handled each.
4. Provide a test plan I can run before letting this touch real data.
5. Ask before any step that sends messages, modifies data, or spends money.

Source: https://usecasesforagents.com/use-case/on-demand-website-screenshot-generator/ via usecasesforagents.com