这个 JSON 类型定义有什么问题？

问：

我有一些代码来创建和验证应该表示标记联合的 JSON 架构。我希望 prop 值是 、 或 ，并且根据该值，对象将包含某些其他 props，例如 或：directionltgtetamountrange

import Ajv from "ajv/dist/jtd"
const ajv = new Ajv()

const Filter = {
    "discriminator": "direction",
    "mapping": {
        "gt": {
            "properties": {
                "amount": { "type": "number" }
            }
        },
        "lt": {
            "properties": {
                "amount": { "type": "number" }
            }
        },
        "et": {
            "properties": {
                "range": {
                    "properties": {
                        "top": { "type": "number" },
                        "bottom": { "type": "number" }
                    }
                }
            }
        }
    }
};

const validateFilter = ajv.compile(Filter);

结果：

Error: schema is invalid: 
data/discriminator must NOT have additional properties, 
data must have property 'ref', 
data must have property 'type', 
data must have property 'enum', 
data must have property 'elements', 
data must have property 'properties', 
data must have property 'optionalProperties', 
data/mapping/gt/properties/amount/type must NOT have additional properties, 
data/mapping/gt/properties/amount must have property 'ref', 
data/mapping/gt/properties/amount/type must be equal to one of the allowed values, 
data/mapping/gt/properties/amount must have property 'enum', 
data/mapping/gt/properties/amount must have property 'elements', 
data/mapping/gt/properties/amount must have property 'properties', 
data/mapping/gt/properties/amount must have property 'optionalProperties', 
data/mapping/gt/properties/amount must have property 'discriminator', 
data/mapping/gt/properties/amount must have property 'values', 
data/mapping/gt/properties/amount must match a schema in union, 
data/mapping/gt must have property 'optionalProperties', 
data/mapping/gt must match a schema in union, 
data must have property 'values', 
data must match a schema in union

我不明白为什么会这样。这里有一个沙盒可以搞砸： https://codesandbox.io/s/ajv-errors-54rdmx