Building Custom Skills for Claude

Why it matters

A Skill is a release artifact as much as a prompt. 2.5 expects you to decide how it is packaged, versioned and attached before a domain procedure reaches production requests.

What to practise

Build three Skills — a financial ratio calculator, brand guidelines, and a financial modeling suite — each a folder with a SKILL.md whose frontmatter carries name and description, plus scripts and resources. Upload them with client.beta.skills.create, attach them through container.skills beside the Anthropic pptx and xlsx Skills, and publish a second version with client.beta.skills.versions.create. Watch the three loading stages: metadata, instructions, then files. Note that every request selects "version": "latest".

How it fits

The exercise practises 2.5.3’s packaging and Skills API delivery. Compare its "latest" selection with 2.5.3’s rule to pin a returned version ID in production, and weigh the Skill against the alternatives in 2.5.4.