Advantages of Webmaster Tool: Easily find back links of your website Broken links What are the keywords you are ranking in search engine ....
# Sitemaps Sitemaps are a great way of telling Google what pages you want to be indexed. Google will index your site regardless of using a sitemap, however, this tool makes it easier for Google to index those pages you want it to. You can exclude pages if you really want to, but you can use a generator to create the XML formatted file. Here are some generators - DMXZone provide a Dreamweaver extension that will build a sitemap for you in the correct format - www.dmxzone.com - Google provide a long list here code.google.com - Google talks about Sitemaps here - www.google.com # Content Analysis One of the things Google hates is duplicate content, even worse is duplicate Titles and Descriptions (These are the important Meta Tags) Webmaster Tools will allow you to see if there are any pages with duplicated titles or duplicated descriptions. This is a very important tool to get the most out of these tags # Web Crawl Diagnostic Once Google has crawled (indexed) your website, you hope all of your pages are visible in the index. This tool can help you find out if Google had problems finding and pages. Obviously, if Google can find a page, it wont be in the search engine listings. This can be bad links, moved content or other easily picked up issues. # External Links This shows all of the links into your website from other pages on the internet. The best thing is the link on the right hand side that allows you to see all of the inbound links. (Note: this does not show all of the times your website is mentioned, only the working links people can click on to find you) In basic search engine terms, the more inbound links the better for you # Geographic Targeting This one is bit more advanced and will affect a smaller number of people. One of the key changes in Google's delivery of search results is the pre filtering that is done when you search. Google will filter your results, even if you don't ask it to. As an example, if you do a search for a topic and DO NOT select the "web pages from this country" button your results are still biased towards the country Google believes you are in. Alternatively, if you select the "web pages from this country" button, you will get results that Google think are directed to that country.
Google Webmaster Tools is a useful tool for reporting statistics and diagnostics pertaining to the management of your site’s pages in Google indexing.
Yeah this pretty much sums it up. If you have a xml sitemap you can also submit it in GWT. Also, I remember having a site hacked with malware and it was necessary to fix the problem inside GWT. So there are various reasons you should use it.
web master tools can act as xml sitemap. Submit your blog in Goggle, yahoo and Bing webmaster tools and surely you will get good benefit from them