from my puppet class mysql-server.pp:

munin::plugin { "mysql_bin_relay_log": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_commands": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_connections": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_files_tables": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_bpool": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_bpool_act": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_insert_buf": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_io": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_io_pend": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_log": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_rows": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_semaphores": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}
munin::plugin { "mysql_innodb_tnx": ensure => "mysql_", script_path => "/usr/local/share/munin-plugins"}

on a puppet run from a host in this class:

[root@gnshard2b ~]# puppetd -tv
info: Loading fact vlan3002_address
info: Loading fact network_address
notice: Ignoring --listen on onetime run
info: Retrieving facts
info: Loading fact vlan3002_address
info: Loading fact network_address
err: Could not retrieve catalog: Invalid parameter 'script_path' for type 'Munin::Plugin' at /etc/puppet/manifests/classes/mysql_server.pp:59 on node gnshard2b.gaggle.net
warning: Not using cache on failed catalog

munin documentation on script_path found @ http://www.masterzen.fr/puppet/rdoc/classes/munin.html