Most often ideas or specifications of how to design toys come from product engineers but the accessibility to play with that toy may not be part of the equation. But partnering with other stakeholders, like physical therapists, provides an opportunity for toys to be designed for as many children as possible to be able to play with it, no matter their abilities. Because of their knowledge of the body and the children receiving their services, physical therapists are a prime resource to provide parameters or specifications a child's physical disabilities. These parameters can then be used by design engineers to work to develop toys that can meet the needs of those children.
As with most inclusive design, it should be something that is easy for anyone to use. Using iterative prototyping to find the best fit solution provides an end result will allow more children an opportunity to enjoy playing.