Splunk REST API - How to add a webhook action?

There are two parameters you need to specify to create a webhook action:

actions='webhook'action.webhook.param.url='http://firewall.mycompany/ban'

Here is your request, modified to include a webhook action:

curl -s -k -u admin:password https://splunk.rf:8089/servicesNS/admin/search/saved/searches > /dev/null \  -d name=bruteforcetest \  --data-urlencode actions='webhook' \  --data-urlencode action.webhook.param.url='http://firewall.mycompany/ban' \  --data-urlencode output_mode='json' \  --data-urlencode alert.digest_mode='0' \  --data-urlencode alert.expires='24h' \  --data-urlencode alert.managedBy='' \  --data-urlencode alert.severity='3' \  --data-urlencode alert.suppress='1' \  --data-urlencode alert.suppress.fields='source_ip' \  --data-urlencode alert.suppress.period='2m' \  --data-urlencode alert_comparator='greater than' \  --data-urlencode alert_condition='' \  --data-urlencode alert_threshold='20' \  --data-urlencode alert_type='number of events' \  --data-urlencode alert.track='1' \  --data-urlencode cron_schedule='* * * * *' \  --data-urlencode description='' \  --data-urlencode disabled='0' \  --data-urlencode displayview='' \  --data-urlencode is_scheduled='1' \  --data-urlencode is_visible='1' \  --data-urlencode max_concurrent='1' \  --data-urlencode realtime_schedule='1' \  --data-urlencode restart_on_searchpeer_add='1' \  --data-urlencode run_n_times='0' \  --data-urlencode run_on_startup='0' \  --data-urlencode schedule_priority='default' \  --data-urlencode schedule_window='0' \  --data-urlencode dispatch.earliest_time='rt-2m' \  --data-urlencode dispatch.latest_time='rt-0m' \  --data-urlencode display.events.fields='["host","source","sourcetype", "source_ip"]' \  --data-urlencode search='"error: invalid login credentials for user"'