How to custom validate on `Meteor, Simple Schema, Uniform (React)`?

help
1

I base on Meteor, Simple Schema, Uniform (React)

// Method
Meteor.methods({
  existName(name) {
    return name == 'Rabbit'
  },
})
--------------
//  Custom Msg
SimpleSchema.setDefaultMessages({
  messages: {
    en: {
      nameExist: 'Name is exist!',
    },
  },
})

// Schema
  name: {
    type: String,
    async custom() {
      const result = await Meteor.call('existValue', this.value)

      if (result) {
        return 'nameExist'
      }
    },
  },
-----------------
// Uniform-Material
....... Code Here ........

But don’t work, please help me
And then I tried to validate on client, It work fine

// Schema
  name: {
    type: String,
    custom() {
      if (this.value == 'Rabbit') {
        return 'nameExist'
      }
    },
  },