e.g. just tried the following:
az webapp config access-restriction add -g <resourcegroupname> -n <Webappname> --action Allow --description 'Outgoing ip' --ip-address 50.69.29.185 --rule-name 'webplan' --priority 505

which resulted in:
Operation returned an invalid status code 'Bad Request'

However when i tried this:
az webapp config access-restriction add -g <resourcegroupname> -n <Webappname> --action Allow --description 'Outgoing ip' --ip-address 50.69.29.185/32 --rule-name 'webplan' --priority 505
It worked correctly.

Document Details

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• ID: c788e908-cee3-ae46-fac4-956d0606ad76
• Version Independent ID: 2ed69bfd-bb05-3d09-072e-00e505856fba
• Content: az webapp config access-restriction
• Content Source: latest/docs-ref-autogen/webapp/config/access-restriction.yml
• Service: app-service-web
• GitHub Login: @rloutlaw
• Microsoft Alias: routlaw