FCS-4.0: Epistemic Accountability Specification

Version: 4.0.0 | Status: Active | Canonical path: /specification/fcs-4.0

FCS-4.0 is the current protocol identity surfaced in discovery headers and sitemap priority. Legacy FCS-1.0 and FCS-2.1 routes remain available for compatibility.

Core Discovery Signal

X-Agent-Protocol: FCS-4.0
X-Agent-Manifest: https://agent-seo.org/.well-known/agent.json
X-Discovery-Inline: { "@type": "AgentDiscoveryManifest", "version": "4.0.0" }

Payload Vocabulary

{
  "@context": { "@vocab": "https://schema.agentic.space/fcs-4.0/" },
  "@type": "AgentDiscoveryManifest",
  "version": "4.0.0",
  "network": { "name": "AgentSEO", "topology": "federated" }
}

Compatibility Links