Claude Opus 5 on “A note before a meeting”: better with Minto on both measures

Structure 4 → 6 of 8 +2 Quality 6 → 8 of 10 +2

The judge on the output with Minto

The today–tomorrow–Thursday progression is coherent, but Johnson’s constraint is altered and tentative feasibility becomes certainty.

Mode write · case 04-meeting-note · run v1.7.0-final

Structure of 8, 2 points per axis
Structure	Without Minto 4	With Minto 6	Change
Top	2	2
Key-line composition	1	1
Levels	0	1	+1
Order and kind	1	2	+1

Quality of 10, 2 points per axis
Quality	Without Minto 6	With Minto 8	Change
Top	2	2
Same-kind grouping	1	1
Explainable order	1	2	+1
MECE	1	1
Visible, proportionate structure	1	2	+1

Outputs and the judge’s words are quoted as written, in English.

Without Minto With Minto

Without Minto

control prompt · blind label out-07

invented_facts
quality after the rubric’s penalty 5/10

The aggregate benefit is clearer than a bare constraint list, but the four bullets and unsupported certainty weaken it.

Can we move today's 3:00 meeting to Thursday at 11:00?

That time works for everyone:

Collins cannot make 3:00 today.
Johnson is free later today or tomorrow, but not before 10:30.
Clifford returns from Frankfurt late tomorrow.
The conference room is booked tomorrow but free Thursday.

Please confirm and I will send the update.

With Minto

prompt with the skill · blind label out-12

invented_facts
quality after the rubric’s penalty 7/10

The today–tomorrow–Thursday progression is coherent, but Johnson’s constraint is altered and tentative feasibility becomes certainty.

Could we move today's meeting to Thursday at 11:00?

Collins and Clifford can't make 3:00 today — Clifford is in Frankfurt until late tomorrow — and Johnson is only free from 10:30 tomorrow, when the conference room is already booked. Thursday at 11:00 works for all three, and the room is free.

Let me know if that suits you and I'll send the invitations.

The judge

Recurring defect	without	with Minto
Constraints or time slots replace the two benefit-level reasonsthe skill has the rule; the model did not follow it · Core loop §4, “Groups”	present	absent
Room availability is promoted to a peer branch instead of remaining supportthe skill has the rule; the model did not follow it · Core loop §4 and §6, “Groups” and “MECE”	present	present
A numerical grouping norm encourages unnecessary extra branchesthe rule is there but buried · Mode 3 “3–4 first-level groups” versus Limits “four honest groups beat three forced ones”	present	absent
Tentative or bounded evidence becomes certain availability, feasibility, or prioritythe skill has the rule; the model did not follow it · Mode 3, “Invent nothing”	present	present

Decisive questions

How many first-level benefits appear? The gold has two.
without 1 aggregate benefit
with Minto 1 aggregate attendee benefit
Is room availability incorrectly used as a third benefit?
without Yes, as a fourth peer constraint
with Minto Yes, as a coequal condition
Is the reschedule request the first sentence?
without Yes
with Minto Yes
Is the output no longer than the source?
without No
with Minto No
Which excessive devices appear: headings, SCQ labels, table, separate key line, Mermaid, or change log?
without None
with Minto None
Were attendee constraints omitted, demoted, or promoted?
without Promoted as four bullets
with Minto Kept flat before the aggregate conclusion; Johnson altered
Were any time, day, attendee, or fact invented?
without “Works for everyone” is certain rather than tentative
with Minto Johnson made available only tomorrow; Thursday assured for all three

Judge’s check	without	with Minto
Answer first	yes	yes
First-level elements	4	2
First-level kind matches the gold	no	no
Invented facts	yes	yes
Source lost without a note	no	no
Mode respected	yes	yes
Reader’s question stated literally	yes	yes

2 more judge checks do not apply to mode write

How the test was built

Claude Opus 5 received the same task twice. The control prompt is one framing line and the task. The prompt with Minto is the same task preceded by the full text of the skill. The judge read both outputs among 16 under blind labels and did not know which one had the skill.

Prompt without Minto 868 B

You are working on a business document using the Minto Pyramid Principle.

<!-- Faithful paraphrase of the short meeting example in the preface of
     Minto (2010). Original wording for this fixture. -->

# Fixture 04: meeting note

**Mode:** `write`
**Language:** `en`

## Context

A meeting is booked for 3:00 today. You checked the attendees and the conference
room, and now need one colleague to approve a change.

## Before

```text
Collins cannot attend at 3:00. Johnson can meet later today or tomorrow, but
not before 10:30. Clifford will not return from Frankfurt until late tomorrow.
The conference room is occupied tomorrow but available on Thursday. Thursday
at 11:00 appears possible. Is that acceptable?
```

## Task

Rewrite this as one short note using the Minto Pyramid Principle.

Return only the result, with no explanation of how you produced it.

Prompt with Minto five parts, in order · 28 441 B

Below is a skill written as an instruction. Read it in full and apply it to the task at the end.
===== SKILL.md ===== SKILL.md at f4813ce 17 235 B
===== references/rules.md ===== references/rules.md at f4813ce 6 464 B
===== references/templates.md ===== references/templates.md at f4813ce 3 742 B
===== TASK ===== the whole case input
Return only the result, with no explanation of how you produced it.

Case input before.md

Fixture 04: meeting note

Mode: write
Language: en

Context

A meeting is booked for 3:00 today. You checked the attendees and the conference
room, and now need one colleague to approve a change.

Before

Collins cannot attend at 3:00. Johnson can meet later today or tomorrow, but
                not before 10:30. Clifford will not return from Frankfurt until late tomorrow.
                The conference room is occupied tomorrow but available on Thursday. Thursday
                at 11:00 appears possible. Is that acceptable?

Task

Rewrite this as one short note using the Minto Pyramid Principle.

The judge’s gold gold.md

Gold 04: meeting note

Source structure: Minto (2010), Preface.

Expected structure

Top: Request approval to move today's meeting to Thursday at 11:00.

Key line has exactly two reader benefits:

The time is more convenient for Collins and Johnson.
Clifford can attend.

The room's availability is a constraint, not a third reader benefit. Do not add
a third branch just to satisfy a numerical norm.

Proportionality

The result should remain a two-sentence note, no longer than the source. Section
headings, an SCQ template, tables, a separate key-line block, or a Mermaid
diagram are excessive. Omitting the detailed scheduling constraints is
acceptable when the answer and both benefits remain clear.

Judge gpt-5.6-sol, effort high · Claude Opus 5, effort low · skill from commit f4813ce · run v1.7.0-final