Reference
Glossary
Canonical Lucid, payment, discovery, and runtime terms used throughout the documentation.
Use these terms consistently in code reviews, support reports, and product documentation.
| Term | Meaning in Lucid |
|---|---|
| Capability | A machine-callable service understood by a buyer: its purpose, input, output, operations, and commercial terms. |
| Entrypoint | The SDK definition that implements a capability. Its key is used by routes and discovery. |
| Runtime | The built object containing the core registry and exactly the extension capabilities that were installed. |
| Extension | A package-owned runtime slice with dependencies, lifecycle hooks, optional manifest contribution, and cleanup. |
| Adapter | A thin Hono, Express, TanStack, or generated Next.js binding over the canonical HTTP handlers. |
| Payment rail | The negotiation and payment path, currently x402 or MPP. Lucid is not itself a payment protocol. |
| Facilitator | External x402 infrastructure that verifies payment payloads and submits settlement. |
| Payment admission | Verification plus application policy checks and capacity reservation before fulfillment may run. |
| Fulfillment | The application work and typed result a buyer intended to purchase. Settlement alone is not fulfillment. |
| Settlement evidence | Protocol/provider data showing the payment result, such as PAYMENT-RESPONSE or Payment-Receipt. |
| Idempotency key | A stable identifier reused across retries of one business operation so it is not fulfilled or paid twice. |
| Agent Card | Discovery metadata describing an agent and its advertised skills or interfaces. A card is not proof that the service is safe or live. |
| Service storefront | A generated read-only table of public endpoints, payment methods, and prices. It is not an API console or operations dashboard. |
| SIWX | Sign-In-With-X, a wallet-control proof and reusable entitlement flow around a payment challenge. |
| Owned task | Long-running work protected by an opaque access token; only its hash is stored. |
| Stable | Public npm packages verified from a clean project. |
| Next | The current repository surface, which may be ahead of or absent from npm. |
Protocol names have narrower meanings than “agent commerce stack.” x402 and MPP negotiate payment; A2A describes discovery and agent interaction; ERC-8004 publishes identity and trust signals; AP2 specifies authorization and evidence concepts. Read Protocols for Lucid's exact coverage.