Cardano Improvement Proposals

CIP 12 - On-chain stake pool operator to delegates communication



Standard format for metadata used in an on-chain communication of stake pool owner towards their delegates.


We define two types of communication metadata, which are distinguished by transaction metadata label as defined in the CIP10 Transaction metadata label registry.


The lack of an on-chain communication standard between a stake pool owner and their delegates.

Work in progress CIP6 already defines an external feed of a stake pool within the extended metadata. However, there is need for a more verifiable on-chain communication standard that will also provide additional cost associated with such communication to prevent its abuse.


As per CIP10 Transaction metadata label registry, we assign:


Metadata are written in JSON format and maximum size of metadata around 16KB.

The root object property is a 3 bytes UTF-8 encoded string representing the ISO 639-3 language code of the content.

key Value Rules
title (required) Title of the communication 64 bytes UTF-8 encoded string
content (required) Content of the communication An array of 64 bytes UTF-8 encoded strings
valid (optional) Slot number the communication becomes valid Unsigned integer
expires (optional) Slot number until the communication is valid Unsigned integer

Metadata JSON schema

The schema.json file defines the metadata.

Metadata example including the transaction metadata label

      "1991": [ {
        "lat": {
          "title": "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do",
          "content": [
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do ",
            "eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut e",
            "nim ad minim veniam, quis nostrud exercitation ullamco laboris n",
            "isi ut aliquip ex ea commodo consequat. Duis aute irure dolor in",
            " reprehenderit in voluptate velit esse cillum dolore eu fugiat n",
            "ulla pariatur. Excepteur sint occaecat cupidatat non proident, s",
            "unt in culpa qui officia deserunt mollit anim id est laborum."
          "valid": 10661033,
          "expire": 10669033
        "eng": {
          "title": "But I must explain to you how all this mistaken idea",
          "content": [
            "But I must explain to you how all this mistaken idea of denounci",
            "ng of a pleasure and praising pain was born and I will give you ",
            "a complete account of the system, and expound the actual teachin",
            "gs of the great explorer of the truth, the master-builder of hum",
            "an happiness. No one rejects, dislikes, or avoids pleasure itsel",
            "f, because it is pleasure, but because those who do not know how",
            " to pursue pleasure rationally encounter consequences."
          "valid": 10661033,
          "expire": 10669033


The format of the content field is required to be an array of 64 bytes chunks, as this is the maximum size of a JSON field in the Cardano ledger. Tools, such as wallets, are required to recompose the content of the message.

The current Cardano protocol parameter for maximum transaction size, that will hold the metadata, is around 16KB.

Backwards compatibility

No backwards compatibility breaking changes are introduced.

Reference implementation

We leave the decisions, such as what and how to display communication messages, up to downstream tools and wallets.

This CIP is licensed under CC-BY-4.0