Build a Competitor Radar That Emails You Only What Changed

What you’re building

A scheduled agent that reads a fixed list of competitor URLs — pricing page, changelog, blog, careers, homepage — summarizes each, compares the summary against what it saw last run, and emails you only the differences, ranked by how much each change threatens you.

No raw HTML parsing. No brittle selectors. Just structured summaries diffed against each other, and a short email that gets to the point.

Why not just scrape their site

Scrapers break the day a competitor redesigns their HTML. Selectors stop matching, the job silently returns nothing, and you stop trusting it within a month.

Instead, let Claude read the rendered page with web search turned on and produce a structured summary. You diff the summaries, not the raw HTML — so a full redesign doesn’t break you, and a subtle pricing change that wouldn’t change the HTML at all still gets caught.

Step 1 — List your targets

Pick 3–5 competitors. For each, collect the 5 URLs that actually signal change:

• Pricing page — tier names, prices, seat limits, annual discount
• Changelog / release notes — what shipped and when
• Blog — what they’re positioning, what problems they’re publicly claiming to solve
• Careers — who they’re hiring tells you their roadmap; a sudden cluster of ML roles is a signal
• Homepage — headline messaging shifts are usually the last thing to change before a major launch

That’s 15–25 URLs total. Paste them into a plain text list — that’s all you need for the next step.

Step 2 — The watch prompt

Give Claude this prompt with your URL list pasted in. Run it with web search enabled so it reads the live pages, not cached versions.

The output is a clean JSON array — one object per URL, a short summary, and a list of signals (e.g. ["new $49 tier", "SOC 2 badge added"]). Save this as radar_state.json. That’s your baseline.

Step 3 — Diff against last week (the important part)

This is where most setups go wrong. People run the watch prompt, read the summaries manually, and miss the change buried in paragraph three. The diff is what turns a 4,000-word page dump into a three-line Monday email.

On each subsequent run, load last week’s radar_state.json alongside the new output and send Claude this prompt:

The diff strips out the noise. You’re not reading 25 summaries — you’re reading only what moved since the last run, with a threat rating already attached.

Step 4 — Put it on a schedule

Run it weekly. Monday morning is ideal — you get the update before the week starts rather than mid-sprint.

• State file persistence: the key is that radar_state.json survives between runs. Store it somewhere it won’t get wiped — a Drive folder, a repo, or a simple file in cloud storage. Each run reads last week’s file and writes this week’s over it.
• Delivery: have the agent email or DM you the diff output directly. A weekly Slack DM or plain-text email with the three-line summary is all you need.
• When to run more frequently: if a competitor is in a visible launch cycle (job postings spiking, blog frequency up, homepage messaging shifted), switch to daily for that competitor until things stabilize.

What good output looks like

One short email, once a week. For example:

• HIGH: Competitor A added a $49 starter tier — undercuts our entry plan by $10/month.
• MEDIUM: Competitor B shipped SSO. That removes one of our enterprise selling points.
• LOW: Competitor C posted two new sales roles. No product signal yet.

Ranked, skimmable, done in 30 seconds. If nothing changed that week, the email says “no significant changes this week” and you move on. The value is in the weeks where something did move — and you knew before your customers told you.