## Overview
Before calling any business API on the Yonyou U8 open platform, the client must obtain a global token. A token lives for 2 hours and can be shared across all business calls; the platform caps token issuance at 2000 per 2 hours, so callers must cache the token locally and only refresh it near expiry.
### Request parameters
1. from_account — the source account assigned to the integration.
2. to_account — the target U8 enterprise account set.
3. app_key / app_secret — issued when the application is created in the U8 open platform console.
4. token — pass the previous token for renewal, or leave empty for the first request.
### Response
errcode 0 means success. The token object carries id (the token value), appKey and expiresIn (seconds). Business APIs are then called with token plus from_account, to_account, app_key and app_secret as URL query parameters.
### Production advice
- The Qeasy U8 connector centralizes the token lifecycle: a singleton cache, proactive refresh five minutes before expiry, and circuit-breaker re-issue on failure — preventing parallel jobs from exhausting the 2000-per-2h quota.
- On-premise U8 deployments require the Yonyou OpenAPI client agent; external systems relay through that agent to the U8 application server.