According to Google Merchant Center Help section with Feed Rules merchants can:
1. Replace field names to supported attribute names from the Google Shopping Products Feed Specification.
For example, if in the feed exported from your shopping cart system your column header is called ''variant_id'' you'll be able to setup a rule to rename it to the supported attribute ''id'' as Google requires it.
2. Replace the values in your feed with values compliant with Google Shopping Products Feed Specification.
Let's say you're selling running shoes for both men and women and you need to submit the gender specification for your products. If in your source feed the gender attributes are called ''men'' and ''women'' you need to transform them to the accepted predefined values for gender: ''male'' and ''female''.
3. Fill in missing attributes with a static value, or with different static values based on conditions.
One of the mandatory fields in your Google Shopping feed is ''condition''. If you're only selling new products this field is probably empty.
If you don't map it, then your products will be disapproved. To solve this problem, you can create a rule that automatically attributes the condition ''new'' to all products.
Feed Rules or DataFeedWatch?
Google Merchant Feed Rules makes many data feed tools with limited functionality & plug-ins that just create an export of your products in Google format, obsolete.
For very small merchants managing limited feeds for Google Shopping only, this tool will turn out to be a time and money saver.
Still, there are plenty of reasons why merchants, especially medium-sized and large ones, will still need to use a data feed management and optimization tool for their shopping campaigns.
Multi-channel eCommerce strategy
Having all your eggs in one basket is never a good strategy and today more than ever it's very important to be wherever your clients are.
That means that you should consider all available channels for your products: shopping channels, marketplaces, comparison shopping engines and affiliate networks in all countries where you have a presence.
If you want to adapt and optimize your data feed for all these channels in a quick and easy way, you'll need to use a feed management tool.
Available category mapping
One of the most important fields in the Google feed is the product category, which ensures that the products show up for the right search queries.
Google wants merchants to use their own taxonomy and they need to match their products to the most specific Google sub-sub category.
Unfortunately, considering how important the category field is in the feed performance, Google Merchant feed rules doesn't support merchants with syncing their products to their mandatory taxonomy.
This means that they need to prepare the categories manually, which is a tremendous hassle.
With DataFeedWatch things are much easier. We have integrated the category mapping, meaning that we are providing merchants with a system that makes a very tedious job, workable.
Create complex and detailed rules
The types of edits that feed rules functionality offers to merchants might be sufficient to small advertisers that only need basic edits to their feeds.
Google enables you to overwrite your values, but you cannot modify just part of your field. For example, if you would like to remove or replace one word from your description, you cannot do that with Google.
Exclude products from your feed
Sometimes you'll sell more by advertising fewer products. By filtering out from the feed the unprofitable, seasonal, out-of-stock and low price products, you improve the quality of the feed and you focus your spending on the most profitable products.
Google Feed Rules doesn't allow you to exclude those products from your feed after you've uploaded them to the Merchant Center.
With DataFeedWatch you have numerous ways to exclude products from the feed based on their prices, profitability, seasonality and other parameters.
Detailed Analytics on individual level
If you have a solid multi-channel strategy in place then you need to constantly review how each channel is performing and which products perform better on a channel or another.
Most of the times CPC campaigns are managed on a category or brand level because most channels will not provide merchants with product level data and also because it's a time-consuming task.
Still, being able to identify best performing products, optimize across channels and review all performance data on a single page will significantly increase the performance of your campaigns.
In short, Google Merchant Feed Rules is a good solution for merchants that advertise on Google Shopping only, have less than few hundred products and want something basic and quick, without getting into much depth with feed management and optimization.
For larger merchants that advertise on various multiple channels and want to be able to fully manipulate their feeds, this functionality isn't sufficient and they need to rely on a sophisticated feed tool to improve their shopping campaigns.