newsletters▌

Drive a sponsor through a SponsorCal booking page — enumerate ad-slot inventory and pricing, pick an available issue date, hand off to Stripe Connect Checkout, then submit assets (headline, body, URL, logo) at the tokenized post-payment URL and track booking status through approval and revisions. Read-only on payment + final asset submission unless caller has explicitly authorized them.

Search Substack for newsletters / publications matching a topic, keyword, category, language, or author and return matching publications with subscriber-tier signals, multi-currency pricing, recent post samples, and canonical URLs as structured JSON. Read-only.