Fetch Substack Stats (Chrome automation)

Table of Contents

• Prerequisites
• Workflow
• Output
• Worked example
• Guardrails

Related skills: Primary alternative to ingest-substack-csv. Produces the same WeekExport contract so downstream skills (compute-baseline, attribute-performance, per-section-tracking) don't care which path produced the data.

Prerequisites

• Chrome logged in to Substack as the publication owner (one-time manual setup by the writer).
• Claude-in-Chrome MCP tools available: tabs_context_mcp, tabs_create_mcp, navigate, get_page_text, read_page, optionally javascript_tool.
• Publication URL known: https://thethinkersnotebook.substack.com/publish/stats (the dashboard URL shape — verify on first run).

Workflow

Per weekly run (Mondays) or on-demand:
- [ ] Step 1: tabs_context_mcp — inspect existing tabs; if a Substack stats tab is already open, reuse; else tabs_create_mcp
- [ ] Step 2: navigate to https://substack.com/publish/stats (or publication-specific dashboard URL)
- [ ] Step 3: get_page_text on the rendered dashboard; parse:
    - Total subscribers (headline number)
    - Weekly delta
    - Posts table with columns: title, date, opens, open rate, clicks, CTR, views, sent
    - Activity-tier distribution (free / paid, active / at-risk / churned)
- [ ] Step 4: For each post in the last 7 days, also navigate to the individual post stats page for:
    - Referral sources breakdown
    - Post-specific engagement
- [ ] Step 5: Normalize into WeekExport object (schema matches ingest-substack-csv's output)
- [ ] Step 6: Archive the scraped stats as CSV in corpus/stats/YYYY-WW.csv (so historical baseline works identically)
- [ ] Step 7: Close the Substack tab (do NOT leave stats pages open in the user's browser)

Step 4 detail — referral sources

Substack exposes referral source breakdowns only on individual post stats pages. The scraper navigates to each outlier post (|z| ≥ 1.0 candidate, determined after baseline compute — so this step may be deferred to attribute-performance) to pull referral data. For non-outliers, per-post referral is skipped.

Output

Same schema as ingest-substack-csv:

{
  "subscribers_end": int,
  "delta_subscribers": int,
  "posts": [
    {"slug", "title", "post_date", "views", "opens", "open_rate", "clicks", "sent", ...}
  ],
  "sends_this_week": int,
  "free_subs": int,
  "paid_subs": int,
  "activity_tier_distribution": {...},
  "source": "chrome-scrape",  # vs. "csv-export" from the other skill
  "scraped_at": ISO8601
}

Written to corpus/stats/YYYY-WW.csv (same archive path as CSV imports). The source field marks provenance so the writer can tell at a glance whether a week came from live scrape or manual export.

Worked example

Trigger: Monday morning, Growth Analyst invokes fetch-substack-stats.

1. tabs_context_mcp — no existing Substack tab.
2. tabs_create_mcp + navigate → Substack dashboard stats page.
3. get_page_text — reads:
   • Total subscribers: 148
   • Weekly delta: +6
   • Posts table (last 7 days): 1 post shown, "Attention is a routing problem", 680 views, 48% open, 5% CTR.
4. For the one post, navigate → post-specific stats → referral breakdown shows 60% direct, 20% Notes, 20% search.
5. Normalize: WeekExport{subscribers_end: 148, delta_subscribers: 6, posts: [...], ...}.
6. Write corpus/stats/2026-W17.csv.
7. Close the Substack tab.

Downstream pipeline (compute-baseline, attribute-performance, etc.) runs identically whether data came from CSV or scrape — the WeekExport contract is stable.

Guardrails

1. Idempotent within a week. If corpus/stats/{YYYY-WW}.csv already exists for today's ISO week, compare — don't overwrite unless the scrape is strictly more recent and differs meaningfully.
2. Close tabs on exit. Do not leave stats pages open in the user's browser; they are distracting.
3. Fallback to CSV cleanly. If any step fails (login expired, dashboard URL changed, page structure shifted), emit fetch-substack-stats FAILED: {reason}; falling back to ingest-substack-csv and halt — let the writer decide whether to retry or drop a manual CSV.
4. Never log individual subscriber emails even though the dashboard subscriber list is visible. Aggregate counts and activity-tier distributions only. Matches the CSV path's privacy posture.
5. Do not navigate anywhere except Substack dashboard URLs. No side-trips.
6. Do not auto-install or update Claude-in-Chrome. If the MCP tools are unavailable, return a specific error ("claude-in-chrome not available; user must enable").
7. Respect soft rate limits. One scrape per week is the default; catch-up mode may run up to 4 if the writer missed multiple weeks, but always space them at least 30 seconds apart.
8. Never take actions on the dashboard. No clicking "Delete", no editing post metadata, no unsubscribing anyone. Read-only.
9. Session state hygiene. If login has expired, do not attempt to log in on the writer's behalf. Halt with login-required message; writer handles auth manually.

Quick reference

• Browser-automation replacement for manual CSV export.
• Same WeekExport contract → downstream pipeline identical.
• Archives to corpus/stats/YYYY-WW.csv on success.
• Fallback: ingest-substack-csv if browser path fails.
• Read-only — never takes actions on the dashboard.