The Purpose of Prototypes

Cagan argues that the main purpose of prototyping is to discover a successful solution, not to ship a product. Recent gen-AI prototyping tools have sharply cut the cost of live-data prototypes, changing the economics that previously limited their use. Most products fail not because they can't be built but because teams never found a solution worth building, meaning it failed the value, usability, feasibility, and viability risks. He explains that required fidelity (visual, behavioral, data) depends on which risk you are testing and which stakeholder you are showing it to. Prototypes also serve as a communication tool for the intended experience, but that is secondary to testing.

01Key takeaways

• Treat prototyping as the core discovery technique, used to test risks before committing to building the real product.
• Ask which of the four risks (value, usability, feasibility, viability) each prototype is meant to test.
• Match prototype fidelity to the specific risk and stakeholder rather than aiming for a single 'just enough' level.
• Recognize that low-fidelity or no-UI prototypes can be ideal for feasibility checks.
• Don't mistake a prototype's value as a communication artifact for evidence that the solution works.
• Build prototyping skills, since they are central to product creation and increasingly assessed in PM interviews.

02Key sections

Purpose of gen-AI prototyping tools

Tools like Lovable, Bolt, and Figma Make have made live-data prototypes cheaper and faster than before. Cagan stresses they are not meant for building production products.

The four product risks

A solution must be valuable, usable, feasible, and viable. Most failures come from missing these risks during discovery rather than from technical building limits.

Fidelity depends on the risk

Visual, behavioral, and data fidelity should be matched to the risk being tested and the stakeholder involved. 'Just enough fidelity' only makes sense in that context.

Building to learn versus building to earn

Discovery is about learning with prototypes, while delivery is about building a production-quality product once the solution is validated.

The prototype as spec

Once validated, a prototype helps communicate the intended experience to engineers, though teams must not confuse this communication role with the testing purpose.

03From the post

“Note: This is part of the product creator series of articles, based on the overview article, The Era of the Product Creator. This series is intended for anyone that wants to create a successful product, whether or not the person has had professional training or experience in product management, product design, or engineering. Overview We... The post The Purpose of…”

04Frameworks mentioned

Summary and takeaways written by PM Atlas; quotes are short excerpts. © the original author.