You're seeing just the function set_purpose, go back to SlackWeb.Channels module for more information.
Link to this function

set_purpose(channel, purpose, optional_params \\ %{})

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Sets the purpose for a channel.

Required Params

  • channel - Channel to set the purpose of
  • purpose - The new purpose ex: My Purpose

Errors the API can return:

  • channel_not_found - Value passed for channel was invalid.
  • is_archived - Channel has been archived.
  • not_in_channel - Authenticated user is not in the channel.
  • too_long - Purpose was longer than 250 characters.
  • user_is_restricted - Setting the purpose is a restricted action.