An agent skill for building developer tools and playgrounds on Val Town. Provides opinionated patterns for creating single-purpose utilities that serve both a human UI and a programmatic API from one HTTP endpoint.

claude skill install https://val-tool-playground-skill.val.run/.well-known/skills/val-tool-playground/SKILL.md

This skill implements the Agent Skills Discovery RFC via well-known URIs.

GET https://val-tool-playground-skill.val.run/.well-known/skills/index.json

Agents can discover and fetch the skill automatically:

GET /.well-known/skills/index.json                                        → skill index
GET /.well-known/skills/val-tool-playground/SKILL.md                      → skill instructions
GET /.well-known/skills/val-tool-playground/references/pico-ui-patterns.md → UI patterns reference

Copy SKILL.md and references/pico-ui-patterns.md into your agent's skill directory.

• SKILL.md — Philosophy (composability, URL-as-interface, raw output, one concern per tool), architecture (dual-mode HTTP handler), visual anatomy, API design, Val Town conventions
• references/pico-ui-patterns.md — Pico CSS v2 base template, tab/input/output patterns, native component catalog, common mistakes

Every tool is a URL. The UI is a convenience layer. The API is the product.