Ravn from Node, with plain fetch

const API = 'https://api.askravn.com/v1/tools/';
const KEY = process.env.RAVN_API_KEY;
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

export class RavnError extends Error {
  constructor(http, code, message) {
    super(http + ' ' + code + ': ' + message);
    this.http = http;
    this.code = code;
  }
}

// Returns results, or null on a free not_found miss.
export async function call(tool, input, { maxWaitSec = 300, tries = 4 } = {}) {
  for (let attempt = 0; attempt < tries; attempt++) {
    const res = await fetch(API + tool, {
      method: 'POST',
      headers: { Authorization: 'Bearer ' + KEY, 'Content-Type': 'application/json' },
      body: JSON.stringify(input),
    });
    if (res.status === 429) {
      const wait = Number(res.headers.get('retry-after') ?? 30);
      const { error } = await res.json();
      if (wait > maxWaitSec) throw new RavnError(429, error.code, 'retry in ' + wait + 's');
      await sleep(wait * 1000);
      continue;
    }
    if (res.status === 503 && attempt < tries - 1) {
      await sleep(2 ** attempt * 1000);
      continue;
    }
    const body = await res.json();
    if (!res.ok) throw new RavnError(res.status, body.error.code, body.error.message);
    return body.status === 'ok' ? body.results : null;
  }
  throw new RavnError(503, 'gave_up', 'retries exhausted');
}

// Example: decide what to do with a signup address
if (import.meta.url === 'file://' + process.argv[1]) {
  const v = await call('validate_email', { email: 'jane@acme.com' });
  if (!v) console.log('no verdict');
  else if (v.status === 'valid' && ['A', 'B'].includes(v.risk_score)) console.log('accept');
  else if (v.status === 'risky') console.log('review:', v.reason);
  else console.log('reject:', v.reason);
}