Is there any APIs for crawling abstract of paper?
Look it up on:


Google Scholar link
Citeseer link


If you get a single exact title match then you have probably found the right article, and can fill in the rest of the info from there.  Both give you download links and bibtex-style output.  What you would likely want to do though to get perfect metadata is download and parse the pdf (if any) and look for DOI-style identifier.

Please be nice and rate-limit your requests if you do this.