The Markdown Service Tools include a Service called “Auto-link web search” which takes selected text, runs a web search on it and creates a Markdown link to the first match for you. The Service recently broke due to changes in DuckDuckGo’s responses.
I think I have it fixed, and have included the updated version in Markdown Service Tools 2.7, available for download below or from the project page. You can update your Services in
~/Library/Services/ by simply unzipping the download and dragging the contents of the created folder into that directory, overwriting what’s there.
Let me know if you still have any trouble with the results or the Service throws errors at you.