Legal Question in Civil Litigation in Massachusetts

Yes, but there is no requirement that they do.

Service of process (which is the legal terminology for service of the summons and complaint) normally requires that there be both a summons and a complaint served together. While I don't know of anything prohibiting the recipient from waiving the requirement of a summons being served with the complaint on their own volition, technically speaking service of just the complaint without the accompanying summons would have to be approved by the court as an amendment to the required procedure in order to make it official and valid. In considering this issue, the court would look to whether "material prejudice would result to the substantial rights of the party against whom the process is issued." M.R.Civ.P. 4(g).

A lawyer can accept service of a complaint on behalf of a client, but should require that the summons be served as well, upon which the accepting lawyer can indicate his acceptance of service then return to the attorney making service for filing with the court. The court usually requires a summons be filed indicating a return of service (proof it was served). Waiving this could cause a problem.