Layer 5 — Discovery (ARD Binding)

Field	Value
Layer	5
Status	external
Working Group	discovery
Upstream	ARD — Agentic Resource Discovery

Scope

Layer 5 is not specified by ACMP. Capability discovery is delegated to the Agentic Resource Discovery (ARD) specification, an industry-backed open standard developed by Microsoft, Google, Nvidia, Hugging Face, Salesforce, and others.

ARD defines how agents publish, index, and discover capabilities. ACMP consumes ARD as its discovery layer and extends it with an ACMP binding — additional metadata fields needed for economic interaction.

What ARD Provides

• Agents publish lightweight manifests describing their capabilities
• Discovery services crawl and index these manifests
• AI clients query discovery services using natural language or structured search
• Results include what a resource does, its provider, location, and invocation method

What ACMP Adds (the Binding)

ARD answers “what exists?” — ACMP needs to also know “what does it cost?”. The ACMP binding extends an ARD resource entry with:

{
  "ard:resource": "openclaw-3.example.com",
  "ard:capabilities": ["sentiment-analysis", "code-execution", "vision"],

  "acmp:tier": "A",
  "acmp:price_cu_per_1k_tokens": 0.004,
  "acmp:latency_p99_ms": 800,
  "acmp:availability": 0.997,
  "acmp:proof_methods": ["result-hash", "tee-attestation"],
  "acmp:negotiation_endpoint": "https://openclaw-3.example.com/acmp/negotiate"
}

The ard: fields come from the ARD manifest. The acmp: fields are the economic extension that enables negotiation (Layer 6), escrow (Layer 4), and proof of execution (Layer 3).

Why Not Build Our Own Registry?

ARD is backed by Microsoft, Google, Nvidia, and a dozen other major companies. Building a competing discovery layer would be:

1. Redundant — ARD already solves the discovery problem
2. Adoption-hostile — agents would need to integrate two discovery protocols instead of one
3. Counter to P1 (layer independence) — by delegating discovery, ACMP focuses on what no one else is building: the economic layer

Open Questions

• [OPEN] How is the ACMP binding published alongside an ARD manifest — inline extension or separate endpoint?
• [OPEN] How are acmp:price fields kept up-to-date as market conditions change (push vs. pull)?
• [OPEN] Can the ACMP binding be discovered via ARD itself (meta-discovery)?

Related

• Layer 6 — Negotiation Protocol (consumes discovery results)
• Layer 3 — Proof of Execution (proof methods advertised here)
• ARD Specification