Extension Development

What it does

When your agent uses it

• Adding features spanning backend and frontend
• Understanding the extension lifecycle
• Needing an architectural overview of how the pieces connect

Example prompts

• “Use the extension-development skill to guide end-to-end feature development in the bootc Podman Desktop extension”
• “/extension-development”

Requirements

• Node.js

Workflow steps

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

1. 1Define API — Add abstract method to packages/shared/src/BootcAPI.ts
2. 2Implement — Add implementation to packages/backend/src/api-impl.ts (see backend-api skill)
3. 3Call from frontend — Use bootcClient.myNewMethod() from /@/api/client (auto-proxied)
4. 4Add route — Add in App.svelte, navigation in Navigation.svelte`
5. 5Add models — Define types in packages/shared/src/models/ if needed
6. 6Build UI — See svelte-ui-design skill for layout and component patterns

What it can do on your machine

Read from SKILL.md and the folder at commit 4230bcf. 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:

  • pnpm

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

• Network

  No URLs in SKILL.md. Its commands use pnpm, which can reach the network depending on how they are called.

  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

Extension Development loads about 1.1k tokens when it runs. Until then it costs about 93 tokens; SKILL.md has 361 words of instructions outside code blocks.

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

~93

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

~1.1k

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 podman-desktop/extension-bootc at commit 4230bcf, republished under its Apache-2.0 licence (© podman-desktop). 361 words, ~1,081 tokens.

name

extension-development

description

Guides end-to-end feature development in the bootc Podman Desktop extension. Covers the extension lifecycle, architecture overview, RPC communication, build system, and extension points. Triggers when adding features spanning backend and frontend, understanding the extension lifecycle, or needing an architectural overview of how the pieces connect.

cat packages/backend/src/extension.ts

pnpm watch  # Watches all packages concurrently

# See all extension points (configuration, menus, commands, views, icons)
cat packages/backend/package.json | grep -A 200 '"contributes"'

telemetryLogger.logUsage('buildDiskImage', { type: 'qcow2', arch: 'arm64' });
telemetryLogger.logError('buildFailed', { error: errorMessage });

© podman-desktop, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/extension-development of podman-desktop/extension-bootc.

Open the folder on GitHubat commit 4230bcf