Hardware PRD Skill

A software PRD can ship wrong and patch later; a hardware PRD is cut into steel and soldered onto boards. This skill writes a PRD that forces the decisions that get expensive after tooling: cost targets with a full stack (not just BOM), certifications named per market, reliability as numbers, and forecast assumptions stated so the supply chain can be sized honestly.

What This Skill Produces

• A complete hardware PRD with numbered, testable requirements (shall-statements)
• A target cost stack: BOM → COGS → landed cost, with margin math
• A regulatory/certification matrix per target market
• Reliability, serviceability, and packaging requirements with acceptance numbers
• Forecast assumptions and the EVT/DVT/PVT milestones the schedule hangs on

Required Inputs

Ask for these if not provided; if the brief is thin, infer sensible values and label each one [assumed — confirm]:

• Product concept and user — what it is, who buys it, key use environment (indoor/outdoor, temp range, drop risk)
• Target retail price and channel — retail vs D2C changes the margin stack
• Target markets — determines the cert list (US, EU, UK, etc.)
• Power source — battery (chemistry, size) vs mains changes safety certs entirely
• Forecast — units for year 1 and lifetime, plus confidence
• Launch window and any hard date (e.g. holiday season)

Cost & Certification Framework

Cost stack — always build all four layers; never let "cost target" mean BOM alone:

Cert matrix — map each market to its certs. Typical starters: FCC Part 15B (unintentional) / 15C (Wi-Fi/BT radio), CE (RED, EMC, LVD), UKCA, safety UL/IEC 62368-1, RoHS/REACH/Prop 65, batteries UN 38.3 + IEC 62133. Flag any radio module choice that lacks modular certification — it adds months.

Reliability targets — state as numbers: MTBF (hours), warranty return rate ceiling (% in 12 months), lifetime (years/cycles), and the abuse cases (1 m drop, IP rating, operating temp range).

Output Format

Hardware PRD: [product]

1. Overview & user — problem, user, use environment
2. Requirements — numbered shall-statements grouped: functional, industrial design (size/weight/CMF limits), environmental
3. Target cost stack — the four-layer table with numbers and margin math
4. Regulatory & certification matrix — market × cert × owner × lead time
5. Reliability & quality targets — MTBF, return-rate ceiling, abuse cases, ORT expectation
6. Serviceability & repair — field-replaceable units, disassembly, spare-parts strategy
7. Packaging — retail vs bulk, drop-test spec (e.g. ISTA 3A), dielines owner
8. Forecast assumptions — Y1/lifetime units, MOQ implications, ramp shape
9. Milestones — EVT/DVT/PVT/MP dates and what each gate must prove
10. Open questions & assumptions — everything labelled [assumed — confirm]

Quality Checks

• Every requirement is testable — a DVT engineer could write a pass/fail test from it
• Cost target includes landed cost and survives the channel-margin math
• Every target market has its certs listed with lead times
• Reliability targets are numbers, not adjectives ("robust" is not a spec)
• Forecast assumptions are explicit enough to size tooling and MOQs against
• Battery products name chemistry and the UN 38.3 / IEC 62133 path

Anti-Patterns

• Do not state a cost target without saying which layer it is — "$40 target" that turns out to be BOM-only kills the margin at landed
• Do not write "certified for global markets" — name each market and each cert
• Do not spec reliability as "high quality" — give MTBF, return-rate ceiling, and abuse cases
• Do not omit serviceability — an unrepairable design is a warranty-cost decision, so make it consciously
• Do not hide forecast uncertainty — tooling cavitation and MOQs are bought against this number
• Do not refuse a thin brief — draft with labelled assumptions and list what must be confirmed before EVT