For AI agents: the complete documentation index is available at https://mfeflow.github.io/mfeflow/llms.txt, the full documentation bundle is available at https://mfeflow.github.io/mfeflow/llms-full.txt, and this page is available as Markdown at https://mfeflow.github.io/mfeflow/errors/E214.md.
mfeflow

    MFEFLOW_E214

    A feature option is invalid.

    Fix

    Pass a value the feature accepts; mfeflow features <name> lists the options.