OTP-002: Contract ABI

The contract’s Application Binary Interface (ABI) defines a format containing information about the contract’s receivers, data structures, getters, etc.

Motivation

ABI is a tool that allows developers to generate handy bindings, UIs, and so on. One of the best consumer usages would be using a DAO and being able to confirm what exactly it is trying to do before signing a transaction.

Specification

ABI is defined as a JSON file, usually with an .abi extension:

{
  "name": "MyContract",
  "types": [
    {
      "name": "StateInit",
      "header": null,
      "fields": [
        {
          "name": "code",
          "type": {
            "kind": "simple",
            "type": "cell",
            "optional": false
          }
        },
        {
          "name": "data",
          "type": {
            "kind": "simple",
            "type": "cell",
            "optional": false
          }
        }
      ]
    },
    // ...etc.
  ],
  "receivers": [
    {
      "receiver": "internal",
      "message": {
        "kind": "text",
        "text": "Vote!"
      }
    },
    {
      "receiver": "internal",
      "message": {
        "kind": "typed",
        "type": "Deploy"
      }
    }
  ],
  "getters": [
    {
      "name": "gas",
      "methodId": 92180,
      "arguments": [],
      "returnType": {
        "kind": "simple",
        "type": "int",
        "optional": false,
        "format": 257
      }
    }
  ],
  "errors": {
    "2": {
      "message": "Stack underflow"
    },
    "3": {
      "message": "Stack overflow"
    }
    // ...etc.
  },
  "interfaces": [
    "org.ton.introspection.v0",
    "org.ton.abi.ipfs.v0",
    "org.ton.deploy.lazy.v0",
    "org.ton.debug.v0"
  ]
}

Drawbacks

• ABI is in JSON format, which is both human and machine-readable, but not the most compact — binary representation could be better, but is not critical for now.

• ABI has no strict JSON or TypeScript schema defined, and thus is subject to frequent changes.

Prior art

• OTP-001: A complementary proposal that provides additional context.