Sendgrid's UI does not give you full control over API keys. This script does. Set two environment variables and you can view your keys, their scopes and add/remove scopes from any key. Simple utility but saves a lot of time and headache.

sendgrid_keys.rb

#!/usr/bin/env ruby

require 'base64'
require 'rest-client'
require 'json'

# https://stackoverflow.com/questions/38613941/sendgrid-error-access-forbidden-when-trying-to-get-user-profile-api
$base_endpiont = "https://api.sendgrid.com/v3/api_keys"

def usage
    exe = File.basename $0
    puts
    puts "Usage:"
    puts "\t#{exe}"
    puts "\t - list keys"
    puts "\t#{exe} [ KEY ID ]"
    puts "\t - view a key's details"
    puts "\t#{exe} [ KEY ID ] add [ SCOPES ... ]"
    puts "\t - add one or more scopes to a key"
    puts "\t#{exe} [ KEY ID ] del [ SCOPES ... ]"
    puts "\t - remove one or more scopes from a key"
    puts
    puts "A list of available scopes can be found here:"
    puts "https://sendgrid.com/docs/API_Reference/Web_API_v3/API_Keys/api_key_permissions_list.html"
    puts
end

def basicAuth
    "Basic #{ Base64.encode64("#{ENV['SENDGRID_USERNAME']}:#{ENV['SENDGRID_PASSWORD']}") }"
end


def get_key(key=nil)
    url = $base_endpiont
    if key
        url += "/#{key}"
    end

    begin
        resp = RestClient.get(url, headers={Authorization: basicAuth})
        JSON.parse(resp.body)
    rescue Exception => e
        puts e
        puts e.response
        exit
    end
end

def save_key(id, key)
    if not key or key['errors']
        puts "Key not found"
        exit
    end
    key.delete('api_key_id')
    key['scopes'].uniq!
    begin
        resp = RestClient.put("#{$base_endpiont}/#{id}", key.to_json, headers={Authorization: basicAuth, 'Content-Type' => 'application/json'})
        JSON.parse(resp.body)
    rescue Exception => e
        puts e
        puts e.response
        exit
    end 
end

def add_scope(id, *scopes)
    key = (get_key id)
    key['scopes'].concat scopes
    res = save_key(id, key)
    print_key res
end

def del_scope(id, *scopes)
    key = (get_key id)
    key['scopes'] = key['scopes'] - scopes
    res = save_key(id, key)
    print_key res
end

def print_key(key)
    if not key or key['errors']
        puts "Key not found"
        exit
    end
    puts "Name: #{key['name']}"
    puts "Key ID: #{key['api_key_id']}"
    puts "Scopes:"
    key['scopes'].each { |scope|
        puts " - #{scope}"
    }
end


case ARGV.size
when 0 then
    res = get_key
    res['result'].each { |key|
        puts "#{key['name']}: #{key['api_key_id']}"
    }
when 1 then
    print_key(get_key ARGV[0])
when 3..100
    case ARGV[1].downcase
    when "add" then
        add_scope ARGV[0], *ARGV.drop(2)
    when "del" then
        del_scope ARGV[0], *ARGV.drop(2)
    else
        puts ">> #{ARGV[1].downcase}"
        usage
    end
else 
    usage
end