Choose a purpose before choosing fidelity
A prototype can help examine handling, demonstrate an interaction, explore an arrangement, or investigate a function. These purposes do not require the same level of detail. A polished appearance may be irrelevant to a mechanism question, while a rough functional rig may not support a meaningful discussion about a finished control layout.
The specification starts with the question the prototype must address. It describes which aspects need to behave realistically and which can be approximated. This creates a practical boundary for the people building the prototype and the people reviewing it.
Make simplifications visible
A demonstrator might use manual input in place of automation, represent a display with a clickable screen, or substitute an available component for an eventual custom part. Those choices can be sensible if their implications are understood.
The document should identify substitutions and explain what they permit someone to examine. It should also identify which conclusions they cannot support. A manual demonstration of a sequence does not establish that a future automated system will meet timing, reliability, or integration requirements.
Describe interfaces and review scenarios
The builder needs to know how the prototype connects to people, equipment, information, and its environment. The specification records important dimensions or conditions when available, expected inputs and outputs, and the behavior required for a review. Unknown values remain open items with a responsible owner.
Review scenarios turn the purpose into a usable activity. They describe who does what, what needs to be observed, and which conditions must be represented. They should include relevant awkward or interrupted situations rather than only a smooth demonstration of the preferred path.
Prepare a useful handoff
The output can include a purpose statement, a fidelity map, functional descriptions, interface notes, review scenarios, and an exclusion list. Any supplied sketches or diagrams need version identifiers so the recipient can tell which instructions belong together.
The specification should be reviewed with the intended builder before a build commitment is made. Availability, safety, cost, and construction details may change what can be represented. A revised scope should preserve the original learning question or explicitly explain why the purpose has changed.
