Native library reference. Extended CLI examples use jacs-compat. This source reference can include unreleased changes; see the package guide for installation and MCP profiles for available tools.

Working with Documents

Documents are the core data structure in JACS. Any JSON object can become a JACS document by adding the required header fields and a cryptographic signature.

What is a JACS Document?

A JACS document is a JSON object that includes:

• Identity: Unique ID and version tracking
• Metadata: Type, timestamps, and origin information
• Signature: Cryptographic proof of authenticity
• Hash: Integrity verification

Creating Documents

From a JSON File

Create a simple JSON document (my-document.json):

{
  "title": "Project Proposal",
  "description": "Q1 development plan",
  "budget": 50000,
  "deadline": "2024-03-31"
}

Sign it with JACS:

jacs-compat document create -f my-document.json

This adds JACS headers and a signature, saves the document, and prints the exact path. Pass --json for a machine-readable document key/path result.

From a Directory

Process multiple documents at once:

jacs-compat document create -d ./documents/

With Custom Schema

Validate against a custom JSON schema:

jacs-compat document create -f my-document.json -s ./schemas/proposal.schema.json

Output Options

# Save to specific file
jacs-compat document create -f my-document.json -o ./output/signed-doc.json

# Print to stdout instead of saving
jacs-compat document create -f my-document.json --no-save

# Verbose output
jacs-compat document create -f my-document.json -v

Document Structure

After signing, a document looks like:

{
  "$schema": "https://hai.ai/schemas/header/v1/header.schema.json",
  "jacsId": "doc-uuid-here",
  "jacsVersion": "version-uuid-here",
  "jacsVersionDate": "2024-01-15T10:30:00Z",
  "jacsOriginalVersion": "version-uuid-here",
  "jacsOriginalDate": "2024-01-15T10:30:00Z",
  "jacsType": "document",
  "jacsLevel": "artifact",

  "title": "Project Proposal",
  "description": "Q1 development plan",
  "budget": 50000,
  "deadline": "2024-03-31",

  "jacsSha256": "a1b2c3d4...",
  "jacsSignature": {
    "agentID": "agent-uuid",
    "agentVersion": "agent-version-uuid",
    "signature": "base64-signature",
    "signingAlgorithm": "ring-Ed25519",
    "publicKeyHash": "hash-of-public-key",
    "date": "2024-01-15T10:30:00Z",
    "fields": ["jacsId", "title", "description", "budget", "deadline"]
  }
}

Required Header Fields

Document Levels

The jacsLevel field indicates the document's purpose:

File Attachments

Attach Files

# Attach a single file
jacs-compat document create -f my-document.json --attach ./report.pdf

# Attach a directory of files
jacs-compat document create -f my-document.json --attach ./attachments/

Embed vs. Reference

# Embed files directly in the document (larger document, self-contained)
jacs-compat document create -f my-document.json --attach ./files/ --embed true

# Reference files (smaller document, files stored separately)
jacs-compat document create -f my-document.json --attach ./files/ --embed false

Attachment Structure

Embedded attachments appear in the jacsFiles field:

{
  "jacsFiles": [
    {
      "jacsFileName": "report.pdf",
      "jacsFileMimeType": "application/pdf",
      "jacsFileSha256": "file-hash",
      "jacsFileContent": "base64-encoded-content"
    }
  ]
}

Verifying Documents

Basic Verification

jacs-compat document verify -f ./signed-document.json

Verification checks:

1. Hash integrity (document hasn't been modified)
2. Signature validity (signature matches content)
3. Schema compliance (if schema specified)

Verify with Schema

jacs-compat document verify -f ./document.json -s ./schema.json

Verify Directory

jacs-compat document verify -d ./documents/

Verbose Output

jacs-compat document verify -f ./document.json -v

Updating Documents

Updates create a new version while maintaining the same jacsId:

jacs-compat document update -f ./original.json -n ./modified.json

The update process:

1. Reads the original document
2. Applies changes from the modified file
3. Increments jacsVersion
4. Links to previous version via jacsPreviousVersion
5. Re-signs with agent's key

Update with Attachments

jacs-compat document update -f ./original.json -n ./modified.json --attach ./new-file.pdf

Extracting Embedded Content

Extract attachments from a document:

jacs-compat document extract -f ./document-with-attachments.json

Extract from multiple documents:

jacs-compat document extract -d ./documents/

Document Payloads

Generic Documents

JACS signs arbitrary JSON payloads through the header schema:

{
  "$schema": "https://hai.ai/schemas/header/v1/header.schema.json",
  "jacsType": "document",
  "content": {
    "subject": "Status update",
    "body": "The requested work is complete."
  }
}

Custom Documents

Any JSON can be a JACS document. Create custom schemas:

{
  "$schema": "https://example.com/schemas/invoice.schema.json",
  "jacsType": "invoice",
  "invoiceNumber": "INV-001",
  "amount": 1000,
  "currency": "USD"
}

Version History

JACS tracks document history through version chains:

Version 1 (jacsOriginalVersion)
    ↓
Version 2 (jacsPreviousVersion → Version 1)
    ↓
Version 3 (jacsPreviousVersion → Version 2)
    ↓
Current Version

Each version is a complete document that can be independently verified.

Working with Multiple Agents

Different Agent Signs Document

# Use a specific agent's keys
jacs-compat document create -f ./document.json -a ./other-agent.json

Verify Document from Unknown Agent

# Verify with strict DNS requirement
jacs-compat document verify -f ./document.json --require-strict-dns

Best Practices

Document Design

1. Use appropriate levels: Match jacsLevel to document purpose
2. Include context: Add descriptive fields for human readability
3. Version control: Keep source files in git alongside JACS documents

Security

1. Verify before trusting: Always verify signatures
2. Check agent identity: Verify the signing agent
3. Validate schemas: Use custom schemas for strict validation

Performance

1. External attachments: Use --embed false for large files
2. Batch processing: Use directory mode for multiple documents
3. Selective verification: Verify only when needed

Common Workflows

Create and Share Document

# 1. Create document
jacs-compat document create -f ./proposal.json -o ./signed-proposal.json

# 2. Share the signed document
# The recipient can verify it:
jacs-compat document verify -f ./signed-proposal.json

Track Document Changes

# 1. Create initial version
jacs-compat document create -f ./contract-v1.json

# 2. Make changes and update
jacs-compat document update -f ./contract-v1.json -n ./contract-v2.json

# 3. Continue updating
jacs-compat document update -f ./contract-v2.json -n ./contract-v3.json

Process Multiple Documents

# Create all documents in a directory
jacs-compat document create -d ./input-docs/

# Verify all documents
jacs-compat document verify -d ./signed-docs/

Next Steps

• Agreements - Multi-agent consent
• Custom Schemas - Create your own schemas