When we choose the tools that we will use to find scholarly articles and information -- library catalogs, databases, websites, and others -- we look at their scope first: subjects, time frame, the types of materials indexed, and the information provided about those materials. Our goal is to understand what is inside the resource, so that we know what information we are able to get out of it. We are matching the resource to our information need. For example, if our research centers around the human factors involved with space flight, would we choose the search in a database that indexes only chemical literature? I hope not!

Evaluating the scope of any resource requires a bit of looking around and a bit of thinking.

What subjects does this resource cover? Does this resource cover the time frame you are looking for? For example, if your research is about the history and future of NASA, and a potential resource contains articles published until 2000, you will need to find a different resource. What types of material are indexed in this resource? Does this resource list articles, eBooks, internet sites, conference proceedings? What information is provided about indexed materials? Do you have access to abstracts only? Can you download a book chapter or the full text of an article? Do you have citation information?

How to evaluate the scope of an information retrieval tool:

Most database lists, like this one from the Florida Institute of Technology's Evans Library, include descriptions written by librarians or other subject experts. Reading these descriptions can tell you a lot about what subjects are indexed.
Think critically about who is providing the resource and why it exists in the first place. For example, tools provided by organizations that focus on engineering will most likely provide materials about engineering.
Check the Help or About Us links within the resource itself, or by reviewing the lists of subjects, genres, or research areas within the resource.
Think critically about the duration of the organization providing the resource. For example, Florida Tech's library has existed since the university was founded, but probably contained some older books as well as new ones at first. Their library also contains some archival materials, such as a rare copy of the Works of Geoffrey Chaucer that was published in 1561. Items are added to the library collection every day, giving their collection a duration of 1958 to the present.
Look around the Advanced Search form. Often, the search fields offered include title, abstract, and full-text, among others, and will tell you that all three items - citation, abstract, and full-text - are indexed in the database.
Look at the options provided on the search results page. Often, results lists will include or link to abstracts, and will display PDF or HTML full-text links if these options are available.
Citations are always included in information discovery resources - this is the information that allows you to search by title, author, date, etc.

Knowing the scope of a database or other information retrieval tool is crucial, but remember that you must always evaluate the items within it to be sure that they are useful to your academic research.