JSON Schemas

JACS schemas now describe a small portable signing surface instead of many narrow workflow document types. The core model is a generic signed JSON document: canonical JSON bytes, a common header, cryptographic signatures, signer identity, hashes, optional files, and optional agreement semantics.

Application-specific payloads belong in the document body or in a custom schema layered on top of the header schema.

Preserved Schemas

Document and Agent Schemas

Schema	Purpose
`header/v1/header.schema.json`	Generic signature wrapper for signed JSON documents
`agent/v1/agent.schema.json`	Agent identity and public signing metadata
`agreement/v2/agreement.schema.json`	Standalone agreement document for verifiable consent to terms
`a2a-verification-result.schema.json`	Cross-language A2A artifact verification result

Component Schemas

Schema	Purpose
`components/signature/v1/signature.schema.json`	Cryptographic signatures
`components/agreement/v1/agreement.schema.json`	Legacy sidecar agreement metadata and co-signatures
`components/files/v1/files.schema.json`	File attachments and content hashes

Configuration Schema

Schema	Purpose
`jacs.config.schema.json`	Agent configuration file format

Schema Locations

Schemas are available as HTTPS URLs and local files:

https://hai.ai/schemas/header/v1/header.schema.json
https://hai.ai/schemas/agent/v1/agent.schema.json
https://hai.ai/schemas/agreement/v2/agreement.schema.json
https://hai.ai/schemas/components/signature/v1/signature.schema.json
https://hai.ai/schemas/components/agreement/v1/agreement.schema.json
https://hai.ai/schemas/components/files/v1/files.schema.json
https://hai.ai/schemas/jacs.config.schema.json

Generic Signed Documents

Every signed document includes a $schema field. Generic payloads use the header schema directly:

{
  "$schema": "https://hai.ai/schemas/header/v1/header.schema.json",
  "jacsId": "550e8400-e29b-41d4-a716-446655440000",
  "jacsVersion": "f47ac10b-58cc-4372-a567-0e02b2c3d479",
  "jacsType": "document",
  "jacsLevel": "artifact",
  "content": {
    "invoice_id": "INV-001",
    "amount": 100.0
  }
}

Custom schemas may extend the header when an integration needs stronger payload validation:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://example.com/schemas/invoice.schema.json",
  "allOf": [
    { "$ref": "https://hai.ai/schemas/header/v1/header.schema.json" },
    {
      "type": "object",
      "properties": {
        "content": {
          "type": "object",
          "required": ["invoice_id", "amount"]
        }
      }
    }
  ]
}

Agreements

Use agreement/v2/agreement.schema.json for new agreement workflows. It is a standalone jacsType: "agreement" document with explicit terms, parties, signer/witness/notary policy, transcript references, links, controllers, and portable verification.

Use components/agreement/v1/agreement.schema.json only when a generic signed document needs simple legacy jacsAgreement countersignature metadata. V1 answers "did these agents approve this payload?" V2 answers "did these agents consent to these terms with this process record?"

HAI Extensions

JACS schemas include a custom hai property that categorizes fields:

Value	Description
`meta`	Metadata fields such as IDs, timestamps, and versions
`base`	Core cryptographic fields such as hashes and signatures
`agent`	Agent-controlled content fields

These categories help determine which fields participate in hashing and signing.

JACS Usage Documentation