Specification Overview¶

Protocol Version: 2026-02-21 | Status: Draft

The Universal Scheduling Protocol (USP) is an open standard that enables consumer platforms and AI agents to discover, check availability of, and book time-based services from businesses. USP supports both paid and free agentic scheduling through two deployment modes.

USP defines three core capabilities -- service catalog, availability, and booking -- along with optional extensions for waitlist management. It supports REST, MCP, A2A, and ESP transport bindings and references IETF standards directly for cross-cutting concerns (security, authorization, error format, idempotency, webhook verification).

Specification Contents¶

Conventions¶

The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this specification are to be interpreted as described in RFC 2119 and RFC 8174. These keywords only carry their special meaning when they appear in all capitals.

Terminology¶

Service Verticals¶

USP defines four core service verticals. The type field on a service MUST be set to one of these values, or to a vendor-defined vertical using reverse-domain notation (e.g., com.wix.services.courses).

Choosing a Deployment Mode¶

Reading Path by Implementer Type¶

Reading Flow¶

The following diagram shows how the specification sections connect and flow between deployment modes:

graph TD
    subgraph domainCore [Domain Core]
        S1["1. Introduction"] --> S2["2. Core Concepts"]
        S2 --> S3["3. Service Catalog"]
        S3 --> S4["4. Availability"]
        S4 --> S5["5. Booking Lifecycle"]
    end

    subgraph discovery [Discovery]
        S6["6. Discovery Registry (Optional)"]
    end

    subgraph ucpPath [UCP-Native Mode]
        S7["7. UCP-Native Mode"]
    end

    subgraph standalonePath [Standalone Mode]
        S8["8. Standalone Mode"]
    end

    subgraph shared [Shared Infrastructure]
        S9["9. Transport Bindings"]
        S9 --> S10["10. Security"]
    end

    subgraph extensions [Extensions]
        S11["11. Extensions"]
    end

    subgraph appendices [Appendices]
        S12["12. Operation Reference"]
        S12 --> S13["13. IANA"]
        S13 --> S14["14. References"]
    end

    S5 --> S6
    S5 --> S7
    S5 --> S8
    S6 -.-> S7
    S6 -.-> S8
    S7 --> S9
    S8 --> S9
    S10 --> S11
    S11 --> S12

Relationship to Other Standards¶

Core Constructs¶

USP is built on three constructs:

Namespace Governance¶

USP uses reverse-domain notation for capability names: {reverse-domain}.{service}.{capability}