On-chain stake pool operator to delegates communication

Created on  by Marek MahutSebastien Guillemot and Ján Hrnko


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

Motivation: why is this CIP necessary?

Stake pool owners and their delegates lack an on-chain communication standard between them.

CIP-0006 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.



We define two types of communication metadata, which are distinguished by transaction metadata label as defined in CIP-0010: Transaction metadata label registry:

  • Message board communication is a type of metadata that has been included in an on-chain transaction between two base addresses associated with a stake pool operator owner address. Given the onetime fee for this communication, we are considering this as a message board of a stake pool, as it also enables delegates to easier access historical metadata communication.

  • Direct delegate communication is a type of metadata that has been included in an on-chain transaction between a stake pool owner account and a delegate's account. This type of communication is more expensive for the stake pool owner, preventing higher abuse and therefore enables wallets to implement notification granularity. It might be suitable for targeting specific delegates, such as messaging only new joined delegates, loyal delegates, high-amount delegates etc.

As per CIP-0010, we assign:

  • Message board communication transaction metadata label 1990,
  • Direct delegate communication transaction metadata label 1991.


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

Rationale: how does this CIP achieve its goals?

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.

Path to Active

Acceptance Criteria

Implementation Plan

  • Develop reference implementation (CIP12 communication tool examples)
  • Offer this standard for implementation in downstream tools and wallets: pending their own decisions about whether and how to display communication messages.

This CIP is licensed under CC-BY-4.0.