---
eip: 2069
title: Recommendation for using YAML ABI in ERCs/EIPs
author: Alex Beregszaszi (@axic)
discussions-to: https://ethereum-magicians.org/t/eip-2069-recommendation-for-using-yaml-abi-in-specifications/3347
status: Stagnant
type: Informational
created: 2017-02-11
---

## Simple Summary

Recommendation for including contract ABI descriptions in EIPs and ERCs as YAML.

## Motivation

In the past, most ERCs/EIPs included an ABI description purely as a Solidity contract and/or interface. This has several drawbacks:
- Prefers a single language over others and could hinder the development of new languages.
- Locks the specification to a certain version of the Solidity language.
- Allows the use of syntactical elements and features of the Solidity language, which may not be well representable in the ABI. This puts other languages at even more disadvantage.

This proposal aims to solve all these issues.

## Specification

The [Standard Contract ABI] is usually represented as a JSON object.  This works well and several tools – including compilers and clients – support it to handle data encoding.

One shortcoming of the JSON description is its inability to contain comments.  To counter this, we suggest the use of YAML for providing user readable specifications.  Given YAML was designed to be compatible with JSON, several tools exists to convert between the two formats.

The following example contains a single function, `transfer` with one input and one output in YAML:

```yaml
# The transfer function. Takes the recipient address
# as an input and returns a boolean signaling the result.
- name: transfer
  type: function
  payable: false
  constant: false
  stateMutability: nonpayable
  inputs:
  - name: recipient
    type: address
  - name: amount
    type: uint256
  outputs:
  - name: ''
    type: bool
```

Specifications are encouraged to include comments in the YAML ABI.

For details on what fields and values are valid in the ABI, please consult the [Standard Contract ABI] specification.

The same in JSON:

```json
[
  {
    "name": "transfer",
    "type": "function",
    "payable": false,
    "constant": false,
    "stateMutability": "nonpayable",
    "inputs": [
      {
        "name": "recipient",
        "type": "address"
      },
      {
        "name": "amount",
        "type": "uint256"
      }
    ],
    "outputs": [
      {
        "name": "",
        "type": "bool"
      }
    ]
  }
]
```

## Rationale

The aim was to chose a representation which is well supported by tools and supports comments. While inventing a more concise description language seems like a good idea, it felt as an unnecessary layer of complexity.

## Backwards Compatibility

This has no effect on backwards compatibility.

## Test Cases

TBA

## Implementation

[yamabi] is a Javascript tool to convert between the above YAML and the more widely used JSON format.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).

[Standard Contract ABI]: https://solidity.readthedocs.io/en/latest/abi-spec.html
[yamabi]: https://github.com/axic/yamabi/