Kansas City is a car city. The main attractions are spread across a wide geographic area — downtown, the Nelson-Atkins/Country Club Plaza area (4 miles south), 18th and Vine (2 miles east), Westport (3 miles south), the sports complex (7 miles east), Swope Park (8 miles southeast) — and public transit connects them unreliably. If you do not have a car, rideshare is the practical alternative.
The streetcar runs a 2.5-mile route between River Market and Union Station with a stop near the Crossroads. It is free to ride and useful for that specific corridor. Cycling is feasible within neighborhoods — the Crossroads, Westport, and the Country Club Plaza area are all bikeable — but the gaps between them involve arterial roads that are unpleasant on a bike. Most visitors find a rental car the most practical option for anything beyond a single-neighborhood stay.
Parking downtown and at most attractions is generally easy and cheap by large-city standards.