-The C<mysql plugin> requires B<mysqlclient> to be installed. It connects to the
-database when started and keeps the connection up as long as possible. When the
-connection is interrupted for whatever reason it will try to re-connect. The
-plugin will complaint loudly in case anything goes wrong.
+The C<mysql plugin> requires B<mysqlclient> to be installed. It connects to
+one or more databases when started and keeps the connection up as long as
+possible. When the connection is interrupted for whatever reason it will try
+to re-connect. The plugin will complaint loudly in case anything goes wrong.
+
+This plugin issues the MySQL C<SHOW STATUS> / C<SHOW GLOBAL STATUS> command
+and collects information about MySQL network traffic, executed statements,
+requests, the query cache and threads by evaluating the
+C<Bytes_{received,sent}>, C<Com_*>, C<Handler_*>, C<Qcache_*> and C<Threads_*>
+return values. Please refer to the B<MySQL reference manual>, I<5.1.6. Server
+Status Variables> for an explanation of these values.
+
+Optionally, master and slave statistics may be collected in a MySQL
+replication setup. In that case, information about the synchronization state
+of the nodes are collected by evaluating the C<Position> return value of the
+C<SHOW MASTER STATUS> command and the C<Seconds_Behind_Master>,
+C<Read_Master_Log_Pos> and C<Exec_Master_Log_Pos> return values of the
+C<SHOW SLAVE STATUS> command. See the B<MySQL reference manual>,
+I<12.5.5.21 SHOW MASTER STATUS Syntax> and
+I<12.5.5.31 SHOW SLAVE STATUS Syntax> for details.