-Once your application is instrumented with `tracef()` calls and
-ready to run, use man:lttng-enable-event(1) to enable the
+For `tracef()`::
+ The optional parameters following 'fmt'.
+
+For `vtracef()`::
+ The 'ap' parameter as the 'ap' parameter of man:vasprintf(3)
+ (`va_list` type).
+
+To use `tracef()` or `vtracef()`, include `<lttng/tracef.h>` where you
+need it, and link your application with `liblttng-ust`. See the
+<<example,EXAMPLE>> section below for a complete usage example.
+
+Once your application is instrumented with `tracef()` and/or `vtracef()`
+calls and ready to run, use man:lttng-enable-event(1) to enable the