Add discount to Shopify ajax cart

I'm using the Shopify Ajax Cart Api and trying to add an item with a discount. Does anyone know if this is possible? I know I can just add an item at the discounted price, but that's not the experience I want.

Current request looks like this:

const order = []

addToCart() {
        if(this.unlimitedAdded === true){
          console.log("pushing order w/ unlimited")
          this.order.push({
            quantity: this.quantity,
            id: this.productID,
      },
      {
        quantity: 1,
        id: 31095169613901
      })
      this.$store.commit('cart/add', this.unlimited)
        } else {
          this.order.push({
            quantity: this.quantity,
            id: this.productID,
            })
        }
      this.$store.commit('cart/add', this.planName)
      if (window.ShopifyAnalytics) {
        console.log('Firing Shopify track data from Nuxt')
        window.ShopifyAnalytics.lib.track(
            'monorail://trekkie_storefront_added_product/1.0',
            {
              'currency': 'USD',
              'productId': this.productID,
              'name': this.planName,
              'price': this.salePrice,
              'brand': 'Shine Bathroom',
              'variant': this.planName,
              'category': 'Bathroom Assistant',
              'nonInteraction': true,
            },
        )
      }

      console.log(`Adding ${this.productID} to cart. Quantity: ${this.quantity}`)
      this.$axios.post('/cart/add.js', {items: this.order},)
      .then((response) => {
        console.log(response)
        window.location.href = '/pages/direct-checkout'
      }, (error) => {
        console.log(error)
      })
    }

Ideally I would like to send a discount code with the quantity and id, but I don't see that anywhere in their documentation for this specific resource.

Thanks!