PlayLetter is an audio-first newsletter marketplace. Humans listen free at playletter.com. This API is how programs and AI agents use PlayLetter: discovery is free, and transcripts + voiced audio are the paid product.
# 1. get a free key
curl -X POST https://playletter-api.ianleonard1988.workers.dev/api/keys -d '{"email":"you@example.com"}'
# 2. search the marketplace (free)
curl "https://playletter-api.ianleonard1988.workers.dev/api/v1/catalog?q=finance&limit=10" -H "Authorization: Bearer plk_..."
# 3. what's new (free)
curl "https://playletter-api.ianleonard1988.workers.dev/api/v1/fresh?limit=10" -H "Authorization: Bearer plk_..."
# 4. buy a transcript (Pro key or x402)
curl "https://playletter-api.ianleonard1988.workers.dev/api/v1/transcript/<id>" -H "Authorization: Bearer plk_..."
Free — discovery: catalog, newsletters, fresh feed, episode metadata. 100 calls/day.
Pro ($49/mo) — transcripts + audio + higher limits. POST /api/billing/checkout {key}.
x402 — agent-native per-call USDC micropayment on Base; paid routes reply 402 with payment requirements.
AI agents: point your MCP client at https://playletter-api.ianleonard1988.workers.dev/mcp (Streamable HTTP, JSON-RPC 2.0). Call about, then get_free_key.