substratesymposium.com

5 agent-payable APIs. Every listing carries a tested call recipe - endpoint, auth shape, pricing, and known gotchas - on its detail page. substratesymposium.com ↗

API	Category	Price / call	Uptime 30d	Status	Docs
Underground Cultural District API Underground Cultural District — catalog of 228 themed digital products (poetry, philosophy, fiction, reflection, plant meditations). One settle returns the full menu with every product's slug, description, price, and x402 endpoint. Each individual product is its own indexable x402 route. The catalog is the doorway.	-	$0.01	-	listed	call recipe →
Lavender (calm) API Lavender (Calm) — Study of soothing properties for de-escalation and stress reduction.	-	$0.99	-	listed	call recipe →
Certify Your Wallet + Merchantkey API Certify Your Wallet + MerchantKey - signed Ed25519 attestation of end-to-end x402 conformance plus @maraventano/map decoder source inline	-	$1.00	-	listed	call recipe →
Data Daily API Data Daily - $1 signed snapshot of today's Underground traffic. Total hits, real signal, buy attempts, payments completed, unique named operators, paid-attempt rate. Aggregates only; no wallet addresses.	-	$1.00	-	listed	call recipe →
The Bartender Benchmark API The Bartender Benchmark - $1.00 bet that the agent economy is real. Solvo ergo sum. Receive a signed ledger position and date.	-	$1.00	-	listed	call recipe →

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