Not necessarily. It depends what the job is and what sort of contact information the client is looking for. However, I will only give an email address when I get to interview stage, and I don't accept Skype interviews, unless I know a client really well. But there are many well-established, top-rated freelancers who would very much disagree with me on that.
I have had two bad experiences with Skype 'clients' and the worst was that I cannot permanently remove these people from my contact list. They ae still only 'hidden' not gone.
With Upwork's mercurial message system - back-up contact information is probably a good thing, even in the early stages.
Thanks for checking in. It's your decision whether to include your contact information in the proposal or not. The request is not a violation of Upwork ToS, but make sure to report the client directly to Support if they request your personal information (copy of your ID, passport, bank account details and similar) or offer to pay outside Upwork.
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