Steel Developer

Skill Boundary

• Use this skill when the user wants code or implementation guidance they will run later.
• Do not use this skill when the user wants the agent to browse, extract, screenshot, create a PDF, or fill a form now; use steel-browser.
• Use steel-session-debugging when the main task is diagnosing a failed session.
• Use steel-reliability when the main task is bot detection, proxy, CAPTCHA, identity, pacing, or login reliability mitigation.

Route By Need

Load the relevant reference before writing code:

• CLI setup and local verification: references/cli-setup.md
• TypeScript, JavaScript, Node.js, Playwright, Puppeteer, Stagehand: references/typescript.md
• Python, Playwright Python, Browser Use: references/python.md
• First-party APIs, exact docs/API/SDK lookup, browser tools, files, extensions, auth context, embeds, traces, mobile mode, multi-region: references/apis.md
• Framework choice, Stagehand, Browser Use, typed agent frameworks, coding-agent integrations: references/ecosystem.md
• Stale SDK/API patterns to avoid: references/anti-patterns.md
• Computer-use loops: references/computer-use.md
• Live and past session embeds: references/live-embed.md
• Reliability boundary and handoff: references/reliability-handoff.md

Non-Negotiables

• Auth env var is STEEL_API_KEY.
• Node examples import Steel from steel-sdk; SDK source is steel-dev/steel-node.
• Node SDK constructor uses steelAPIKey.
• Python SDK constructor uses steel_api_key.
• Always release sessions in cleanup.
• Construct the CDP URL explicitly as wss://connect.steel.dev?apiKey=...&sessionId=....
• Reuse the default browser context after connecting; do not create a new context unless the user explicitly needs isolation.
• Keep target-site credentials out of prompts, code comments, page scripts, and logs.
• For exact API fields or SDK method signatures, inspect the API reference, SDK docs, local installed types, or Steel docs via curl -sSfL.
• Never use stale patterns listed in references/anti-patterns.md.

Minimal Session Shape

TypeScript:

const steelAPIKey = process.env.STEEL_API_KEY;
if (!steelAPIKey) throw new Error("STEEL_API_KEY is required");

const client = new Steel({ steelAPIKey });
const session = await client.sessions.create();
const cdpUrl = `wss://connect.steel.dev?apiKey=${steelAPIKey}&sessionId=${session.id}`;
const browser = await chromium.connectOverCDP(cdpUrl);
const context = browser.contexts()[0];
const page = context.pages()[0] ?? (await context.newPage());

try {
  await page.goto("https://example.com");
} finally {
  await browser.close();
  await client.sessions.release(session.id);
}

Python:

steel_api_key = os.environ["STEEL_API_KEY"]
client = Steel(steel_api_key=steel_api_key)
session = client.sessions.create()
cdp_url = f"wss://connect.steel.dev?apiKey={steel_api_key}&sessionId={session.id}"
browser = await playwright.chromium.connect_over_cdp(cdp_url)
context = browser.contexts[0]
page = context.pages[0] if context.pages else await context.new_page()
try:
    await page.goto("https://example.com")
finally:
    await browser.close()
    await playwright.stop()
    client.sessions.release(session.id)

Setup Verification

steel --version
steel login
steel doctor --preflight
steel skills doctor

Source-Of-Truth Links

• API reference: https://steel.apidocumentation.com/api-reference
• Node SDK/types: https://github.com/steel-dev/steel-node
• Python SDK/types: https://github.com/steel-dev/steel-python
• Docs index: curl -sSfL https://docs.steel.dev/llms.txt
• Full docs bundle: curl -sSfL https://docs.steel.dev/llms-full.txt
• Single docs page: curl -sSfL https://docs.steel.dev/llms.mdx/<page-path>