Revisiting the Product Spec

Cagan argues the traditional product spec is broken: it takes too long to write, is rarely read, leaves hard questions unresolved, and gives false comfort that the product is on track. He proposes replacing it with a single master high-fidelity prototype that covers the full user experience, behavior, and visual design, supplemented by use cases and a wiki for release and platform requirements. Because the prototype can be tested with real users for usability and desirability before engineering begins, problems surface early. He contends this approach reduces churn and rework during engineering, so time to market gets shorter, not longer.

01Key takeaways

• Replace long text specs with a high-fidelity prototype that captures the actual user experience and behavior.
• Prototype nearly all screens and major use cases, faking back-end processing where the experience stays believable.
• Test the prototype with target users for usability and desirability before handing anything to engineering.
• Keep one master spec, with supplemental requirements and use cases in a wiki, to avoid version confusion.
• Resolve hard questions during design, not during engineering, to reduce churn and shorten time to market.

02Key sections

The problem with current specs

Specs come in many names and formats, but most are slow to write, seldom read, and incomplete. Their mere existence can mislead managers into believing the project is healthy.

Requirements for a useful spec

A good spec must capture the full user experience, accurately describe software behavior, serve many consumers, evolve with decisions, and exist as one master representation.

High-fidelity prototypes as the spec

Cagan advocates prototyping nearly all screens and major use cases in a realistic form, faking back-end behavior where the user experience stays plausible. Paper prototypes are rejected for all but trivial interfaces.

Supplementing the prototype

Release requirements like performance and platform support, plus use cases, are documented separately, ideally in a wiki for a single source of truth with Q&A and change history.

Testing and time to market

A prototype can be tested for usability and desirability before engineering starts. This front-loads hard decisions, avoiding costly churn and buggy releases, so overall time to market shrinks.

03From the post

“A partnership dedicated to teaching best practices to product teams and product leaders”

04Frameworks mentioned

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