I read the Documentation to add custom slash commands. It gives an example of a valid JSON response, see https://docs.mattermost.com/developer/slash-commands.html#creating-integrations-with-commands.
The documentation then says "As mentioned previously" several times when speaking of the JSON payload. But every previous description eventually refers to Slack and its proprietary JSON payload format. So if Slack changes its JSON format and adds or removes fields I have no idea if this is gonna work in Mattermost.

Could you please add a page in the documentation which describes the format? Which fields are available? What fields differ from Slack? etc. And then add a link to this page on the „Slash command“ page.

Thanks!