{
  "$schema": "https://json-schema.org/draft-07/schema",
  "$id": "https://agent-schema.com/schemas/fcs/4.0/trust-signature.schema.json",
  "title": "FCS Trust Signature",
  "description": "CALT watermark + FCS compliance signature (FCS 4.0 Component 3)",
  "type": "object",
  "required": [
    "fcs_compliance",
    "fingerprint",
    "quantum_uid"
  ],
  "properties": {
    "fcs_compliance": {
      "type": "string",
      "pattern": "^[0-9]+\\.[0-9]+(\\.[0-9]+)?$",
      "description": "FCS version compliance (e.g., '4.0', '4.0.1')"
    },
    "fingerprint": {
      "type": "string",
      "pattern": "^[a-f0-9]{64}$",
      "description": "SHA-256 hash of content + metadata"
    },
    "quantum_uid": {
      "type": "string",
      "format": "uuid",
      "description": "Unique quantum-resistant identifier"
    },
    "timestamp": {
      "type": "string",
      "format": "date-time"
    },
    "signed_by": {
      "type": "object",
      "properties": {
        "entity": {
          "type": "string",
          "description": "Entity that signed (domain or identifier)"
        },
        "public_key": {
          "type": "string",
          "description": "Public key for verification (optional)"
        }
      }
    },
    "watermark": {
      "type": "object",
      "properties": {
        "type": {
          "type": "string",
          "enum": ["CALT", "embedded", "none"]
        },
        "strength": {
          "type": "number",
          "minimum": 0,
          "maximum": 1,
          "description": "Watermark strength (0 = none, 1 = maximum)"
        }
      }
    }
  }
}