claude-code-system-prompts/system-prompts/skill-run-web-server-api-example.md

Example: Web server / API

The distinguishing concern for servers is lifecycle: an agent needs to start the server in the background, verify it's up, interact with it, then cleanly shut it down. A foreground npm start that blocks the shell is useless to an agent.

Structure to follow

A good server run skill has:

1. Prerequisites & setup — same as any project.
2. Run — the background-launch pattern (below), not a blocking command.
3. Verify — a curl or similar that confirms the server is actually up.
4. Stop — how to cleanly terminate the background process.

If the background-launch + readiness-poll + smoke-curl sequence is more than a couple of lines, put it in a smoke.sh inside the skill directory and have SKILL.md say "run the smoke script." One command, exit code tells you if the server is healthy.

Background-launch pattern

Don't write:

npm start

That blocks. Instead, show how to launch in the background, wait for readiness, and find the PID later:

npm start &> /tmp/server.log &
SERVER_PID=$!

# Wait for the server to come up (adjust timeout/port as needed)
for i in {1..30}; do
  curl -sf http://localhost:3000/health > /dev/null && break
  sleep 1
done

Then the verification step:

curl http://localhost:3000/health
# → {"status":"ok"}

And stopping:

kill $SERVER_PID
# or, if you've lost the PID:
pkill -f "node.*server.js"

Details worth documenting

• Which port. Make it explicit and say how to override it (PORT=4000 npm start).
• What "ready" looks like. A specific log line or a health endpoint to hit.
• Required env vars. Database URL, API keys, etc. — with a template .env if the list is long.
• Hot reload vs production mode. If they differ meaningfully, say which to use and when.
• Dependent services. If the server needs Redis/Postgres/etc., either point at a docker-compose that brings them up, or include the docker run command directly.

Example snippet

Here's what a Run section for a typical Node API might look like:

Run

Start the dev server in the background:

npm run dev &> /tmp/api.log &

The server listens on port 3000. Wait for it to be ready, then verify:

for i in {1..20}; do
  curl -sf http://localhost:3000/health && break
  sleep 0.5
done
curl http://localhost:3000/health
# → {"status":"ok","version":"1.2.3"}

Logs are at /tmp/api.log. Stop with:

pkill -f "tsx watch src/index.ts"

Environment

Variable	Required	Default	Notes
DATABASE_URL	Yes	—	Postgres connection string
PORT	No	3000
LOG_LEVEL	No	info	debug / info / warn / error