**Problem**: Needed to generate an avatar, called the already-installed nano-banana-pro skill — execution failed.

**Cause**: The skill depends on the `GRSAI_API_KEY` environment variable, which was never checked during installation and had never been configured.

**Solution**: Abandoned that skill, used the Gemini native API instead. Afterward, audited all other installed skills for environment variable dependencies and filled in the missing ones.

**Prevention**: After installing a new skill, immediately run a "dependency check" — read SKILL.md, list all required environment variables, confirm each one is configured.

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**Principle**: Installed ≠ usable. A skill's "usable state" needs to be verified, not assumed. Best practice: run a smoke test immediately after installing.