Why does Product Requirements Document (PRD) matter?
Building is the expensive part, and most of what goes wrong in it was decided, or left undecided, before the first line of code. A PRD forces the decisions that are cheap on paper and costly in code: which problem this solves, which customer it is for, what is deliberately out of scope, and what result would count as success. At a startup it is rarely a long document. Its value is that the founder, the engineers, and increasingly an AI coding agent all work from the same written intent instead of three different memories of a conversation.
What does Product Requirements Document (PRD) look like in practice?
Suppose a founder wants to add team accounts to a product that today has single users. A one-page PRD might say: the problem is that customers share one login and lose track of who changed what; the first version covers invites and two roles, owner and member; billing per seat is explicitly out of scope; success is that a quarter of active accounts invite a second person within a month. That last line turns a vague feature into a testable bet, and the out-of-scope line is what stops the build from quietly doubling in size.
What are the common mistakes with Product Requirements Document (PRD)?
- Writing the solution and skipping the problem, so nobody can tell later whether a simpler build would have done.
- Leaving out what is out of scope. Scope grows in whatever direction the document is silent.
- Defining no success measure, which makes it impossible to say whether the feature worked.
- Treating it as a contract that cannot change. A PRD records current intent and should be updated when the evidence changes.
Related concepts
- User StoryA one-sentence description of a piece of work from the user's point of view, usually written as: as a type of user, I want to do something, so that I get some benefit.
- Feature PrioritizationThe discipline of deciding what to build next using explicit, comparable criteria, rather than by whoever asked most recently or most loudly.
- Minimum Viable Product (MVP)The smallest thing you can build that produces a real answer to the riskiest question about your business, not the smallest version of the product you intend to build.
- Build vs. BuyThe decision whether to create a capability yourself or use an existing product or service for it, weighed on cost, speed, control, and whether it is part of your advantage.
- Usability TestingWatching real people try to complete real tasks with your product, without helping them, to see where they get confused or stuck.