Evidence-based PRDs: keep the customer quote attached to every requirement

Open any PRD that's older than a quarter and you'll find a graveyard of requirements with no surviving rationale. "Add bulk export." "Make onboarding shorter." "Support SSO." Each line was once anchored to a real customer in real pain. By the time an engineer picks up the ticket, that anchor is gone, and what's left is a guess dressed up as a spec.

An evidence-based PRD fixes this by keeping the "why" physically attached to the "what." Every requirement carries the customer quote that justifies it, and that quote links back to a verified source, a specific moment in a specific interview. The rationale doesn't live in someone's memory or a Slack thread that scrolled away. It travels with the requirement, down into the task, and stays readable months later when someone asks the only question that matters: why are we building this?

Why rationale evaporates

The decay is structural, not careless. A PM hears something painful in a call, writes a tidy requirement, and the summarizing strips the texture. The exact words, "I export to CSV every Friday and re-key half of it by hand," become "improve export." Three weeks later the requirement is groomed into a ticket, the ticket is scoped down to fit a sprint, and the original voice is now four hops removed from the code being written.

Each hop is a place where intent quietly changes. The engineer who builds "improve export" can't tell whether the user wanted scheduled exports, more formats, or just fewer manual steps. So they pick the interpretation that's easiest to build. That's not a process failure. It's the predictable result of separating a requirement from its evidence.

What an evidence-based PRD actually contains

The structure is simple: a requirement is never allowed to stand alone. Next to "Users need scheduled CSV exports" sits the quote that earned it a place in the doc, and the quote is a link, not a paraphrase. Click it and you land on the exact line in the transcript, with enough surrounding context to confirm it wasn't cherry-picked.

This does two things at once. It forces honesty up front. If you can't find a real quote, the requirement is a hunch and should be labeled one. And it preserves the texture that makes a requirement buildable. "Re-key half of it by hand" tells an engineer the problem is manual data entry, not file format. The verb in the customer's sentence is often the whole spec.

Carry the citation into the task, not just the doc

Most teams stop at the PRD. The doc has citations; the Jira ticket has a one-line title. That's the gap where rationale dies, because work happens in the task, not the doc. The fix is to push the quote one level deeper, into the acceptance criteria and the task itself, so the engineer (or the coding agent) reads the customer's words at the moment of implementation.

When the "why" rides shotgun with the "what," trade-offs get smarter. An engineer who knows the user re-keys data manually will reach for a different solution than one who reads "improve export." And reviewers can check the build against the evidence instead of against their own assumptions. The acceptance criterion stops being "export works" and becomes "the Friday re-keying problem is gone."

Evidence-based PRDs and coding agents

This matters more now that a coding agent is often the one reading the task. Agents are literal. They build precisely what the prompt says and nothing the prompt forgot. Hand one a stripped requirement and you get a stripped feature, fast. Hand it a requirement with the customer quote and the constraint attached, and the rationale shapes the implementation instead of getting lost in translation.

The catch is memory. Your agent forgets everything between sessions; the next prompt starts from zero. So the evidence can't live only in the chat. It has to live in a durable artifact the agent reads each time. That's the job an evidence-based PRD does well: it's the persistent context an agent doesn't carry on its own. In Klyr, a Build Pack is exactly this, a PRD plus acceptance criteria plus a coding-agent prompt, with the source quotes threaded through all three so the "why" survives into the generated code.

How Klyr keeps the why attached

Klyr builds the chain so you don't maintain it by hand. Interviews and notes get synthesized into themes where every claim links to a verified source quote, and themes that can't muster at least two citations are auto-dropped, so weak signal never becomes a requirement. Those cited themes feed a ranked Feature Bet, the Bet becomes a Build Pack, and the citations ride the whole way down. You can see a live cited report end to end.

The honest limit: citations alone are table stakes now. NotebookLM and most coding agents can link a claim to a quote for free, and if all you want is a footnoted summary, you don't need a new tool; here's the comparison without the spin. What's hard, and what actually preserves rationale, is keeping the link intact across the whole loop: from raw quote to shipped task to the outcome you learned, and remembering it next quarter when the same problem resurfaces. That persistent evidence-to-outcome graph is the part your agent can't hold and a static PRD can't either.

The payoff: requirements you can defend

An evidence-based PRD changes the kind of conversation you have. "Why are we building this?" stops being answered with "I think someone asked for it" and starts being answered with a quote and a link. Prioritization debates get shorter because the evidence is on the table, not in someone's head. And six months later, when a requirement looks wrong, you can trace it back and see whether the world changed or the build drifted, instead of arguing from memory.

Keeping the customer's words attached to every requirement and task isn't extra ceremony. It's the difference between a spec you can defend and a guess you have to relitigate. The "why" is the most valuable thing in the room when you make a product decision. Don't let it fall out of the document the moment the decision gets written down. If you want to try the loop, start free.

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