| UUID | uuid | string | true | Unique UUIDv1 identifier for the envelope. |
| Digest | dig | dsig.Digest | true | Digest of the canonical JSON body. |
| Stamps | stamps | array of head.Stamp | | Seals of approval from other organisations that can only be added to non-draft envelopes. |
| Links | links | array of head.Link | | Links provide URLs to other resources that are related to this envelope and unlike stamps can be added even in the draft state. |
| Tags | tags | array of string | | Set of labels that describe but have no influence on the data. |
| Meta | meta | cbc.Meta | | Additional semi-structured information about this envelope. |
| Notes | notes | string | | Any information that may be relevant to other humans about this envelope |
