Searching for items is the most common thing to do on MercadoLibre. Here you can see different search criteria. The API provides programmatic access to the search.
There are a number of tools to complete and refine your search. You can add words in the search text field to refine your search by text query (1). Also, you can search by categories (2) following the category path. In order to refine results you can search using filters (3). To retrieve data you can search by paging (4). To search in a given order, you can sort your results (5)
For more information about search options, you can check this website: https://api.mercadolibre.com/sites/MLA/search/