slack api rtm.start missing_scope needed client

You have to do it before you get the token.

when you do the initial request to connect the app, include &scope="identify,read,post,client"

Under App Credentials get your Client ID and Client Secret. Goto:

https://#{team}.slack.com/oauth/authorize?client_id=#{cid}&scope=client

replacing #{team} and #{cid} with your values.

When you approve the authorization you’ll goto that real url that doesn’t resolve. Copy the whole url to your clipboard and paste it into a text file. Extract out just the “code” part.

Now goto:

https://#{team}.slack.com/api/oauth.access?client_id=#{cid}&client_secret=#{cs}&code=#{code}"

And you’ll get back a token like: xoxp-4422442222–3111111111–11111111118–11aeea211e

(from here: https://medium.com/@andrewarrow/how-to-get-slack-api-tokens-with-client-scope-e311856ebe9)