The requires block in SKILL.md supports 3 dependency types. requires.bins lists command-line binaries like ffmpeg or docker. requires.env lists environment variables your skill reads at runtime. requires.config lists keys from your OpenClaw config file.
You can also set primaryEnv to tell OpenClaw which environment variable is the main credential. When you run openclaw skills check, the output flags any missing primaryEnv value first. For binaries, you can add an install field with platform-specific install commands so you know exactly how to fix a missing dependency.