This topic covers pay‑per‑use and account‑free API patterns emerging to power AI agents across marketplaces, frameworks, and tool stores. By combining metered cloud APIs (Google Cloud, AWS) with payment rails—crypto-native flows like Solana Pay.sh and fiat/crypto processors such as Stripe and Coinbase—developers can expose agent functionality with per‑resolution pricing or microtransactions while avoiding traditional account signups and subscription gates. These patterns matter in 2026 because agent ecosystems have matured: marketplaces and tool stores need granular monetization, lower onboarding friction, and composable billing that supports both serverless and client‑side execution. Key technical approaches include wallet‑based, signed payment receipts for account‑free access; server validation and replay protection; and routing layers that proxy requests to multiple model providers or billing backends. Important tradeoffs to manage are privacy, anti‑fraud/KYC requirements, latency and cost predictability. Representative tools and roles: Perplexity AI supplies web‑grounded, real‑time answers and APIs useful for sourced agent responses; AskCodi provides an OpenAI‑compatible routing layer and developer tooling to run custom models across providers; Replit hosts and orchestrates web‑native agents and assistants; Tate‑A‑Tate enables no‑code agent construction and publishing; Crescendo.ai illustrates managed, per‑resolution enterprise CX where human/AI hybrids use per‑outcome fees. Together these tools show how marketplaces, frameworks, and tool catalogs can integrate pay‑per‑use and account‑free flows to reduce friction and enable new microeconomies for agents—while requiring careful attention to compliance, UX, and billing transparency.