Gems are gone.
Your skill
still loads.

Gemini said yes to the upload, then couldn't load it

Gems are being retired: personal accounts lose them on 2026-12-17, Workspace accounts in 2027. Gemini skills take the same SKILL.md folders as every other AI, so the obvious move is to upload the skill. On 2026-10-23 that broke two ways. A skill with fonts was refused outright ("unsupported file type"), and a skill whose upload succeeded failed in chat ("the skill failed to load") because it held a Markdown file in references/.

Seven test skills settled it: Gemini loads SKILL.md and images, nothing else. This tool reshapes any skill to fit.

Point it at a folder

• python3 tools/agent-skill-to-gemini-skill/agent-skill-to-gemini-skill.py path/to/skill --out dist/gemini writes dist/gemini/<name>/ and <name>.zip. Upload the zip in Gemini under Customize → Skills → Upload, then call it with @name.
• Too many files? Add a .geminiignore to the skill (gitignore-style globs, ! re-includes) or pass --exclude GLOB.
• Exit 1 means a rule is broken; each one is printed with a ✗.
• Test: sh tools/agent-skill-to-gemini-skill/agent-skill-to-gemini-skill.test.sh.

What it won't do

• It doesn't rewrite instructions. "Run scripts/x.sh" still says so, and Gemini's sandbox has no network.
• It doesn't host images. More than 99 need ignoring or a home on the web.
• It doesn't upload. Gemini has no skill API; you upload the zip.
• PDFs are kept as files but weren't tested at load time.
• The rules are a snapshot of Gemini build 20261022.15. A real upload is the final test.

Where it lives

One skill folder, end to end

convert(src, out, excludes) in agent-skill-to-gemini-skill.py does it in one pass.

1. List. source_files() runs git ls-files -z in the skill; outside a repo it walks the folder. is_junk() drops .DS_Store, Thumbs.db, desktop.ini, ._* and __MACOSX/; ignored() applies .geminiignore then --exclude, last match wins.
2. Sort. Extensions in KEEP (images, PDF) stay files. Anything else that decodes as UTF-8 is inlined; the rest is dropped and named on stderr.
3. Inline. Each text file becomes ## FILE: <path> plus a fenced block, the fence one backtick longer than any run inside it. A one-line note above the body tells the model to read those sections where it names a path.
4. Check. NAME_RE on the name, then the file count against 100, total bytes against 104857600, and each remaining extension against ALLOWED, the 47 read from Gemini's upload code.
5. Write. <out>/<name>/ is replaced, and the zip gets the folder at the top with every entry stamped 2026-01-01, so the same skill always yields the same bytes.