Trace context carries the identifiers needed to relate spans across processes. At an outgoing boundary, inject context into the request or message carrier; at the receiving boundary, extract it before creating the next span.

Propagation topics

General guidance

Use the OpenTelemetry propagator API supplied by the language SDK rather than parsing or constructing headers by hand. Confirm both sides use compatible propagators and that each intermediary preserves the required carrier fields.
Trace headers are correlation metadata, not a place for credentials or business secrets. Apply the application’s trust policy when accepting context from external callers, and do not put sensitive values in propagated baggage.