Can you show me an example Netdata custom monitor configuration where a command line tool provides the metric?
Here is an example Netdata custom monitor configuration using a command line tool to provide metrics:

[my_cmd_tool] 
update_every = 10 
priority = 60535 
command = /path/to/my/cmd/tool.py 

[my_cmd_tool_metric1] 
source = my_cmd_tool 
chart_type = gauge 
format = %percentage% 
unit = % 

[my_cmd_tool_metric2] 
source = my_cmd_tool 
chart_type = line 
format = %counter% 
unit = items 

This will run the /path/to/my/cmd/tool.py script every 10 seconds, and will create two Netdata charts using the metrics it provides - a gauge chart for my_cmd_tool_metric1 and a line chart for my_cmd_tool_metric2.

The script itself would output metrics like this:
 percentage=75 
 counter=12345

And Netdata will pick them up to create the charts.

Let me know if you have any other questions!
Where do I need to put this configuration?