docker-compose/compose/config/fields_schema_v2.json

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "id": "fields_schema_v2.json",

  "properties": {
    "version": {
      "enum": [2]
    },
    "services": {
      "id": "#/properties/services",
      "type": "object",
      "patternProperties": {
        "^[a-zA-Z0-9._-]+$": {
          "$ref": "service_schema_v2.json#/definitions/service"
        }
      },
      "additionalProperties": false
    },
    "volumes": {
      "id": "#/properties/volumes",
      "type": "object",
      "patternProperties": {
        "^[a-zA-Z0-9._-]+$": {
          "$ref": "#/definitions/volume"
        }
      },
      "additionalProperties": false
    }
  },

  "definitions": {
    "volume": {
      "id": "#/definitions/volume",
      "type": "object",
      "properties": {
        "driver": {"type": "string"},
        "driver_opts": {
          "type": "object",
          "patternProperties": {
            "^.+$": {"type": ["string", "number"]}
          },
          "additionalProperties": false
        }
      }
    }
  },
  "additionalProperties": false
}