x-n8n-url: https://n8n.example.com
x-n8n-key: n8n_api_key_here
x-instance-id: optional-instance-id
x-session-id: optional-session-id

1. Request arrives with headers
2. Extract n8n credentials from headers
3. Validate credentials against n8n instance
4. Create or resume session
5. Execute MCP tool with tenant context
6. Return response

interface Session {
  id: string;
  n8nUrl: string;
  n8nApiKey: string;
  instanceId?: string;
  createdAt: Date;
  lastUsedAt: Date;
}

const key = `rate:${apiKey}:${hour}`;
const count = await kv.get(key) || 0;
if (count >= limit) {
  throw new RateLimitError();
}
await kv.put(key, count + 1, { expirationTtl: 3600 });