Start From the Number, Not the Demo
The demo is easy: paste a document, get a plausible paragraph, watch the room nod. The roadmap review is where AI ideas actually die. Six features were proposed last quarter, and the two worth building were the ones where someone in the room could name the number that moves — already recorded in a system nobody had to invent for the occasion.
Strong use cases read like this:
- Support reply drafter — share of tickets resolved with no human edit to the draft. Baseline today: 0%, everything is manual.
- Contract intake — minutes from email arrival to fields sitting in the ERP. Baseline: 14 minutes.
- Search reranking on the store — conversion rate on sessions that used search. Baseline: 3.1%.
Weak ones read like "AI copilot for the whole team" with no metric attached. Copilots can be fine products; the problem is that without a baseline, the launch meeting cannot separate improvement from vibes.
Two candidates on one page
| Candidate | Metric | Baseline | 60-day target | Where the evidence comes from |
|---|---|---|---|---|
| Ticket reply drafter | % resolved with the draft accepted unchanged | 0% (all manual) | 45% | acceptance logged by the agent UI |
| Invoice field extraction | fields correct on first pass | 62% manual keying | 90% | audit of 200 invoices |
| Meeting-notes summarizer | minutes saved per meeting | not measured | 4 min | self-report survey — weak |
The first two have logs that already answer "did it work." The summarizer's survey will be argued about for a month. Prefer candidates whose success or failure is written down by systems that exist.
The metric myopia trap
Optimizing one number invites damage to the next. Acceptance rate climbs if the drafter quietly handles only easy tickets — selection bias wearing a good dashboard. Extraction accuracy climbs if the model abstains on everything hard and abstentions are counted as safe. Pair every primary metric with one counter-metric — escalation rate, abstain rate, or a sampled quality review — before launch, and the pairing becomes the metric definition you can hand to Online Metrics for AI Features later. Which shape the feature takes in the first place is decided in Common LLM Application Archetypes.
Feasibility Is Three Questions
A demo answers "can a model do this." Feasibility answers whether your feature can do it under your constraints, and the constraints are always the same three.
1. Data availability
What will the feature read? If the policies exist, are current, and can be retrieved, the project is buildable this quarter. If the knowledge lives in three people's heads and a 2019 Confluence page, the project is a content project first and an AI project second. If you need labeled examples to measure success and none exist, the eval set is part of the scope, not homework — building without it means the launch meeting argues instead of measures.
2. Latency tolerance
Ask what the user is doing while waiting:
| User context | Comfortable total latency | Design consequence |
|---|---|---|
| Inline suggestion as they type | ~200–500 ms | small model, streaming, prefix caching |
| Chat turn | 1–3 s before first token feels slow | flagship is fine if it streams |
| Batch job over a document set | minutes are fine | biggest model, parallelized |
A four-second model is fine for a nightly digest and fatal for a keystroke-driven suggestion. Set the budget first — it eliminates half the candidate models before anyone argues about quality.
3. Acceptable error rate
Price the wrong answer:
- Wrong paragraph tone → cheap; regenerate.
- Wrong invoice amount posted to an ERP → dollars plus an audit finding.
- Wrong medical, legal, or financial statement → the reason those domains carry heavier evaluation and human oversight (Responsible AI Foundations).
Worked check. Invoice intake at 3,000 invoices a day. Manual keying costs about $0.35 per invoice to verify, and a wrong field costs roughly $40 to unwind downstream. At those prices a 5% field-error rate is survivable if flagged rows go to a human; a 20% rate is not, no matter how cheap the API call is. The constraint that fails first — data, latency, or error cost — decides what you build, and it is usually cheaper than the constraint everyone expected.
Risk Tiers and the Manual Prototype
Before a pipeline gets built, run the workflow by hand. People play the model's part for a week or two: users fill in the form the "AI" will eventually read, a human drafts the answers behind the scenes, and delivery looks identical to the shipped feature.
This measures the two things a demo cannot: do users actually submit inputs, and are human-drafted outputs accepted? Teams that skip it frequently automate a feature nobody uses, then discover during the postmortem that the inputs were never being supplied in the first place. The manual week costs a product manager's time; the abandoned pipeline costs a quarter.
proposal
|
+--> metric named + baseline known? -- no --> rewrite the idea
|
+--> data / latency / error cost OK? -- no --> lighter feature, or data work first
|
+--> risk tier
| low --> automate, sample quality in production
| medium --> human approves before the output leaves the building
| high --> human decides; model drafts with citations only
|
+--> manual prototype, 1-2 weeks
+--> usage and acceptance hold --> automate
+--> nobody submits --> stop, cheaply
The risk tier sets how much oversight the feature owes its users, and impact is the only thing that sets it. A tone-degrading summary needs spot checks. A refund denial or an account lock needs a human approving before the customer sees anything. Credit, medical, and legal outcomes need a human decision, with the model confined to drafting and citing. What disclosure and appeal path ride along with those tiers is covered in Responsible AI Foundations, and the scoring you did in this topic is the input to it.
Quiz
1. Three AI ideas reach review. Which one is ready to build?
2. A feature shows suggestions as the user types, and the comfortable budget is roughly 300 ms. Which factor most constrains your model choice?
3. A proposed feature gives medical dosage advice directly to end users. What does its risk tier require?
4. What is the main question a manual, human-behind-the-scenes prototype answers before automation is built?
Flashcards
Question
What three things must a strong use case name before it is built?
Click to reveal answer
Answer
A success metric (resolution rate, time saved, conversion lift), a baseline measured today, and an evidence source that records outcomes without a new survey.
Question
What are the three feasibility constraints, and what does each rule out?
Click to reveal answer
Answer
Data availability (rules out features whose knowledge or labels do not exist yet), latency tolerance (rules out models too slow for the interaction), acceptable error rate (rules out automation where a wrong output costs more than the feature saves).
Question
What is metric myopia and how do you counter it?
Click to reveal answer
Answer
Optimizing one number while quietly damaging another — accepting only easy tickets to lift acceptance rate, or abstaining everywhere to lift accuracy. Pair the primary metric with a counter-metric such as escalation rate, abstain rate, or sampled quality review.
Question
Why prototype a use case manually before automating it?
Click to reveal answer
Answer
A human performing the model's role for a week or two proves users will submit inputs and accept outputs, at the cost of a product manager's time instead of a quarter of engineering.
Question
How does risk tier affect oversight?
Click to reveal answer
Answer
Low impact: automate with sampled quality checks. Medium: a human approves before output ships. High (credit, medical, legal): a human decides, with the model drafting and citing only.
Revision Notes
Key Takeaways
- 1. A use case is ready when it names a metric, a baseline, and an evidence source that already records outcomes
- 2. Feasibility is data, latency, and error tolerance — the first constraint to fail decides what you build
- 3. Every primary metric needs a counter-metric, or the feature will be optimized into a different failure
- 4. Risk tier sets oversight: automate the annoyances, approve the costly, keep humans deciding the consequential
- 5. A manual prototype validates demand for the cost of a week, before a quarter of automation is spent
Interview Tips
- • Pitch any AI idea as metric → baseline → target → evidence source; interviewers listen for the baseline, not the model choice
- • When asked how you scope feasibility, walk data, latency, and error cost in that order and say which one kills weak ideas first
- • Expect "how would you validate this before building?" — answer with the manual prototype and the two questions it answers
- • For high-stakes examples, name the oversight explicitly: who approves, what the user sees, and how a wrong output is corrected
Cheat Sheet
Identifying Valuable AI Use Cases — Cheat Sheet
Gate 1 — Metric
- Name the number: resolution rate · time saved · conversion lift · first-pass accuracy
- Baseline from existing logs, not a survey
- Counter-metric paired (escalation / abstain / sampled review)
Gate 2 — Feasibility
| Constraint | Ask | Fails when |
|---|---|---|
| Data | Does the knowledge or label set exist and stay current? | knowledge lives in people's heads |
| Latency | What is the interaction budget? | model slower than the budget (typing = 200-500 ms) |
| Error cost | What does one wrong output cost to unwind? | cost of error > value of automation |
Gate 3 — Risk tier
low -> automate + sample quality
medium -> human approves before it ships
high -> human decides; model drafts with citations
Gate 4 — Manual prototype
Run the workflow with humans as the model for 1-2 weeks:
inputs submitted? outputs accepted? If yes, automate. If no, stop cheaply.
Common failure: idea selected for demo wow with no baseline; then acceptance metric gamed by only handling easy cases.
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