Deno Frontend Development

What it does

When your agent uses it

• Starting a Vite, Astro or Next.js app under Deno
• Building a server-rendered Fresh app with islands
• Migrating a Fresh 1.x project to 2.x
• Working out why a framework fails under Deno permissions

Example prompts

• “Create a new Vite React app with Deno and get the dev server running.”
• “Add an interactive counter island to my Fresh project and keep its props serializable.”
• “Migrate this Fresh 1.x project to 2.x.”

Requirements

• Deno installed

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1Islands ship JavaScript — keep them small, leave everything else in
2. 2Island props must be serializable. Functions cannot be passed.
3. 3Handlers take a single (ctx) parameter.

What it can do on your machine

Read from SKILL.md and the folder at commit d5f6ace. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • deno
  • npm

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • fresh.deno.dev

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Deno Frontend Development loads about 783 tokens when it runs, and up to ~3.5k if it reads all its reference files. Until then it costs about 84 tokens; SKILL.md has 299 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~84

When it runs · the whole SKILL.md, loaded when a task matches

~783

With references · SKILL.md plus every file in references/, read only if the agent opens them

~3.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from denoland/skills at commit d5f6ace, republished under its MIT licence (© denoland). 299 words, ~783 tokens.

name

deno-frontend

description

Use when building a web frontend with Deno — running React, Vite, Astro, SvelteKit, Next.js, Nuxt or other npm frameworks under Deno, or working with Fresh, Deno's own island-architecture framework. Covers which path to pick, Fresh 2.x routes, handlers, islands, Preact signals, Tailwind, and Fresh 1.x to 2.x migration.

license

MIT

metadata.author

denoland

metadata.version

3.0

deno create vite my-app     # or astro, next, nuxt, svelte…
cd my-app
deno install
deno task dev

deno run -Ar jsr:@fresh/init
cd my-project
deno task dev                # http://localhost:5173

// islands/Counter.tsx — interactive, ships JS
import { useSignal } from "@preact/signals";

export default function Counter() {
  const count = useSignal(0);
  return <button onClick={() => count.value++}>Count: {count.value}</button>;
}

© denoland, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (references) in skills/deno-frontend of denoland/skills.

• SKILL.md
• references/FRESH.md
• references/FRESH_MIGRATION.md

Open the folder on GitHubat commit d5f6ace