yasufumi-nakata/Elsevier_skill — reverse-engineered prompt

Build me a small Python command line helper for working with Elsevier research APIs. I want to set my Elsevier API key once in an environment variable, then run simple commands from the terminal to search for papers, fetch a paper abstract when I have a DOI, and get a basic research trends summary for a field across selected years.

Keep it simple and useful for a researcher who doesn’t want to write API calls by hand. The search command should accept a plain text query and a result count. The abstract command should accept a DOI. The trends command should accept a field name and a few years, then summarize what it finds in a readable way.

Please include clear setup instructions, a requirements file or project config, and a short README with examples. Add helpful error messages for missing API keys, bad inputs, or API failures. Look up the current Elsevier API docs online if you need to.