A number of tools can be used to generate citation templates algorithmically. The functionality is built into the VisualEditor and RefToolbar. Citation bot can be run on a page, perhaps summoned by the Citation expander gadget. The user scripts reFill (formerly reflinks), ProveIt, and ReferenceExpander are able to generate citations from a url.
This can be a great timesave, but the citations are not always correct or complete. Cautious editors will always double check the output of these tools to verify the correctness and completeness of the generated citations, but even very experienced editors may place too much trust in the tools, and create citations that must be repaired or cleaned up afterwards.