{
  "product": {
    "attribute_set_id": 4,
    "type_id": "simple",
    "sku": "B201-SKU",
    "name": "B201",
    "price": 25,
    "status": 1,
    "custom_attributes": {
      "description": "Heavy Duty Brake Cables",
      "meta_description": "Some describing text"
    }
  }
}

$productData = [
        "attribute_set_id"  => 4,
        "type_id": "simple",
        "sku": "B201-SKU",
        "name": "B201",
        "price": 25,
        "status": 1,
        "custom_attributes" => [
                ["attribute_code" => "description", "value" => "Heavy Duty Brake Cables"],
                ["attribute_code" => "meta_description", "value" => "Some describing text"],
                ["attribute_code" => "image", "value" => "/w/i/sample_1.jpg"],
                ["attribute_code" => "small_image", "value" => "/w/i/sample_2.jpg"],
                ["attribute_code" => "thumbnail", "value" => "/w/i/sample_2.jpg"]

            ]
    ];

{
    "product": {
      "attribute_set_id": 4,
      "type_id": "simple",
      "sku": "B201-SKU",
      "name": "B201",
      "price": 25,
      "status": 1,
      "custom_attributes": {
        "description": "Heavy Duty Brake Cables",
        "meta_description": "Some describing text",
        "image" : "/w/i/sample_1.jpg",
        "small_image": "/w/i/sample_2.jpg",
        "thumbnail": "/w/i/sample_3.jpg"
      }
  }
}

{
  "product": {
    "media_gallery_entries": [
      {
        "media_type": "image",
        "label": "someimagelabelhere",
        "position": 0,
        "disabled": false,
        "file": "http://mymagentosite.com/pub/media/catalog/product/d/7/image.jpg",
        "content": {
          "base64_encoded_data": "string",
          "type": "string",
          "name": "string"
        },
      }
    ],
  }
}