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Assumption Mapping skill

List the assumptions behind an idea and rank them by importance and evidence. Use when a plan feels solid and you need to find the beliefs it rests on before you commit.

$npx alyn-cli add assumption-mapping
View this skill on GitHubdeanpeters/Product-Manager-Skills/skills/assumption-mapping/SKILL.md
Pack stars
8,019
Pack installs
166k
Alyn Score
72/99
Updated
2 days ago

deanpeters

Assumption Mapping

What is the Assumption Mapping skill?

Assumption Mapping is a product management skill by deanpeters for Claude Code, Cursor, Codex and other AI coding agents. List the assumptions behind an idea and rank them by importance and evidence. Use when a plan feels solid and you need to find the beliefs it rests on before you commit.

Find the beliefs your idea silently depends on, rank them, and pick the few worth testing first.

When to use it

Use when a plan feels solid and you need to find the beliefs it rests on before you commit.

What the SKILL.md covers

  • Purpose
  • Input
  • Key Concepts
  • What an Assumption Is
  • Five Kinds of Risk
  • Generating Them: Ask "What Would Have to Be True?"
  • Importance by Evidence
  • Evidence Is What Happened, Not What Was Said
  • Pick the Few, and Name What Would Change Your Mind
  • Facilitation Source of Truth
Author
deanpeters
Pack
deanpeters/Product-Manager-Skills (30 skills)
Category
Product management, #82 of 185
Alyn Score
72 / 99
Files
4, includes references
License
Not stated
Last updated
2 days ago
Works with
Claude Code, Claude, Cursor, Codex, Gemini CLI, Copilot

Assumption Mapping compared to similar skills

SkillAlyn ScoreGitHub starsUpdated
Assumption Mapping · deanpeters728k2 days ago
Identify Assumptions Existing · phuryn7828k7 days ago
Product Manager · Corey Haines619124 days ago
Foundation Build Risk Review · product-on-purpose688052 days ago

Install Assumption Mapping

Pick your agent. Every command is ready to paste.

$npx alyn-cli add assumption-mapping

Detects your agents (Claude Code, Cursor, Codex and 70+ more) and installs to the right folder. Add -g to install globally.

$npx skills add deanpeters/Product-Manager-Skills --skill assumption-mapping

Or use the open skills CLI directly.

01

Install it

Run the command above, or upload the folder in Claude.

02

Ask naturally

Describe the task. Your agent loads assumption-mapping when the request matches its description.

03

Name it if needed

If it does not trigger, say “use the assumption-mapping skill”. In Codex, type $assumption-mapping.

The skill itself

SKILL.md

FolderGitHub

Assumption Mapping

Purpose

Find the beliefs your idea silently depends on, rank them, and pick the few worth testing first.

Every plan is a stack of assumptions: customers have this problem, they'll notice our solution, they'll pay for it, we can build it, the channel will carry it. Most are fine. A few can sink the idea, and the dangerous ones are usually the ones nobody wrote down because they felt like facts.

The sentence to keep in your head: you don't need to test everything, you need to test the assumption that would hurt most if it were wrong and that you know least about.

It sits between discovery and de-risking: research-synthesis tells you what you've learned, this skill tells you what you're still taking on faith, and the Define skills (pol-probe-advisor, derisk-measurement-advisor) test it.

Input

Works best with: The idea or plan, and the decision it supports (build it, fund it, launch it).

Also useful: The business case, the research you have, the customer and segment, and who must believe the plan for it to go ahead.

Anything supplied with the invocation itself (text after the skill name, a pasted context dump, or an appended ARGUMENTS: line) counts as answers already given. Use it and skip whatever it covers; don't re-ask.

Arriving empty-handed? That works too. The skill opens by asking what the idea is and what has to be true for it to work, and builds the list from your answers. Assumptions it adds itself are tagged as suggestions for you to confirm.

Example invocations:

  • Assumption map for the Route Optimizer add-on. Business case says 15% attach in year one.
  • What are we assuming in the NFA-500 migration plan? Decision: fund the bracket kit.

Key Concepts

What an Assumption Is

A statement you believe that the plan needs to be true, and that you have not verified. Written as a testable claim, not a worry: "Dispatchers will try the optimizer without a training session," not "adoption might be hard."

Five Kinds of Risk

Sort each assumption by the kind of way the idea could fail:

Type The question Example
Desirable Do customers want it, and does it solve a problem they feel? Dispatchers feel the rescheduling pain weekly
Usable Can they actually use it without help? A dispatcher can optimize a day in under five minutes
Viable Does it work for the business: revenue, cost, channel, legal? Resellers will sell an add-on for a 15% margin
Feasible Can we build and run it? Routing runs under two seconds at peak load
Ethical Could it cause harm or break trust? Technician location data is acceptable to technicians

Four of these come from the common product-risk framing (value, usability, viability, feasibility). The fifth is added here because AI and location-data products fail on it, and nobody writes it down. See recommendation-canvas and lean-ux-canvas for related framings.

Generating Them: Ask "What Would Have to Be True?"

Walk the idea as a story, from first contact to payment to long-term use, and at each step ask what has to be true. Do it by role (the user, the buyer, the person who builds it, the partner who sells it) because each sees different risks. Include the boring ones (a team will actually have time to do this; legal will approve). Boring assumptions sink more ideas than clever ones.

Importance by Evidence

Place each assumption on two axes:

  • Importance: if this is wrong, does the idea fail? (high = it does)
  • Evidence: what do we actually have? (strong = observed or measured; weak = opinion)
Strong evidence Weak evidence
High importance Monitor. You know enough. Test first. This is the leap of faith.
Low importance Ignore Park it. Revisit if the idea changes.

The top-right cell is the work. Everything else is either known or doesn't matter yet.

Evidence Is What Happened, Not What Was Said

Rank evidence by how close it is to real behavior: observed behavior and paid usage beat stated intent, which beats expert opinion, which beats your own conviction. "Everyone I talked to loved it" is weak evidence unless they paid, scheduled, or did something that cost them. Label what you hold as Fact, Inference, or Assumption, as in autonomous-investigation.

Pick the Few, and Name What Would Change Your Mind

For each top assumption, state the kill condition: what result would make you change or stop. Without it, the test only reassures. Then hand the top two or three to a test: pol-probe-advisor for a proof-of-life probe, derisk-measurement-advisor for how to measure it.

Facilitation Source of Truth

Use workshop-facilitation as the interaction protocol when running this conversationally. Assumption mapping works well as a short team workshop: individuals write assumptions alone first, then the group places them.

Default entry mode: Guided · set in pm-skills.config.yaml (library-wide default or a per-skill override); the user's own choice in the session always wins. On the first turn, offer all three modes, then open in the default without waiting for a pick: Guided asks the first question, Context dump invites the paste, Best guess asks for a one-sentence minimum and drafts with every assumption labeled.

Anti-Patterns (what this is NOT)

  • Not a risk register. Risks are worries; assumptions are testable claims the plan needs.
  • Not a test plan. It chooses what to test. The Define skills design the test.
  • Not a verdict on the idea. It shows what's unproven, not that the idea is wrong.
  • Not a list of everything. Thirty assumptions ranked is useful; a hundred is noise.

Application

Use template.md for the scaffold.

Output convention. Artifact first: the assumptions table, the map, the top three with kill conditions. Commentary short, after. Tag each assumption [FROM YOU], [RESEARCH], or [AI-SUGGESTED, VALIDATE THIS], and record evidence only if you can name it. Evidence you can't point to is "none."

If the PM brings a list, critique first. Are they testable claims or worries? Is every risk type represented, or only desirability? Are the boring ones present? Is evidence behavior or opinion? Name gaps; offer rewrites last.

Step 1: Frame the Idea and the Decision

What the idea is, who it is for, and what decision it supports. The decision sets how much evidence is enough.

Step 2: Generate Assumptions

Walk the story by role, asking what must be true. Include boring ones. Write each as a testable claim and tag its risk type.

Step 3: Rate Importance and Evidence

For each, mark importance (does the idea fail if wrong?) and evidence (what do we actually hold, named). Be harsh on evidence: opinion is weak.

Step 4: Map and Choose

Place on the map. Pick the high-importance, weak-evidence assumptions. Choose the top two or three, and write a kill condition for each.

Step 5: Hand Off and Hand Back

Point each top assumption to a test skill. Close with a short summary (supplied, inferred, unknown) and a numbered ladder, evidence-favored first, labeled (Recommended): probe the top assumption this week; gather evidence for two more before deciding; run the map as a team workshop; or stop if a top assumption already looks fatal.


Examples

See examples/sample.md (Fieldlight Route Optimizer, SaaS) and examples/sample-industrial.md (Northfield NFA-500 migration). Both show the boring assumption being the one that matters.


Common Pitfalls

Pitfall 1: Only Desirability

Symptom: Every assumption is "customers will want it." Consequence: The idea passes a demand test and dies on cost, channel, or legal. Fix: Walk all five risk types by role.

Pitfall 2: Worries Instead of Claims

Symptom: "Adoption might be hard." Consequence: Nothing to test and no way to know when it's settled. Fix: Restate as a testable claim with a threshold.

Pitfall 3: Opinion Counted as Evidence

Symptom: "Strong evidence: the team is convinced." Consequence: The riskiest belief looks safe. Fix: Evidence is behavior or data you can name. Otherwise it's none.

Pitfall 4: Testing What's Easy

Symptom: The team tests the cheap assumption, not the dangerous one. Consequence: Progress that changes no decision. Fix: Test the high-importance, weak-evidence one first.

Pitfall 5: No Kill Condition

Symptom: The test has no result that would change the plan. Consequence: It only ever reassures. Fix: Write what result stops or changes the idea before running it.

Pitfall 6: Skipping the Boring Ones

Symptom: No assumptions about capacity, legal, support, or sales readiness. Consequence: The idea fails on the item nobody listed. Fix: Ask each role what must be true for them.


References

Skill Files

External Frameworks

  • Assumption mapping, leap-of-faith assumptions: Eric Ries, The Lean Startup; David J. Bland and Alex Osterwalder, Testing Business Ideas.
  • Four product risks: Marty Cagan, Inspired.
  • Importance by evidence: a widely used 2x2 in lean product practice.

Provenance

Distilled from practitioner experience running assumption workshops and de-risking plans.

Tips for Assumption Mapping

  • • Start a fresh session after installing so your agent picks up the new skill.
  • • It bundles reference files. The agent reads them only when needed, so they cost no context until then.
  • • It is part of a pack with 30 skills. Install only the ones you need with --skill to keep triggers precise.
  • • If two skills overlap, mention the one you want by name.

Questions about Assumption Mapping

What does the Assumption Mapping skill do?

List the assumptions behind an idea and rank them by importance and evidence. Use when a plan feels solid and you need to find the beliefs it rests on before you commit.

How do I install Assumption Mapping?

Run "npx alyn-cli add assumption-mapping" in your project. The Alyn CLI installs it for Claude Code, Cursor, Codex and 70+ other agents. In Claude on the web, upload the skill folder as a ZIP under Customize > Skills.

Does Assumption Mapping work in Cursor and Codex?

Yes. Assumption Mapping uses the open SKILL.md format, so it works in Claude Code, Claude, Cursor, OpenAI Codex, Gemini CLI, GitHub Copilot and other agents that support agent skills.

When should I use the Assumption Mapping skill?

Use when a plan feels solid and you need to find the beliefs it rests on before you commit.

What is inside the Assumption Mapping skill?

The SKILL.md covers Purpose, Input, Key Concepts, What an Assumption Is, Five Kinds of Risk, Generating Them: Ask "What Would Have to Be True?", and the skill folder has 4 files.

What is a good alternative to Assumption Mapping?

Identify Assumptions Existing by phuryn is the highest-ranked similar skill from another creator, with an Alyn Score of 78 compared to 72 for Assumption Mapping.

Is Assumption Mapping free?

Assumption Mapping is open source on GitHub. It is free to install; check the license before commercial use.

Who made Assumption Mapping?

Assumption Mapping is published by deanpeters in the deanpeters/Product-Manager-Skills repository, together with 29 other skills.

Similar skills. From other creators.