Skill Series (03): Skill Design Patterns — 5 Patterns That Make Output Predictable

Five Dimensions of a Skill

Every Skill can be designed and audited across five dimensions:

Skill = When (trigger condition)
      + Who  (role declaration)
      + What (task objective)
      + How  (execution steps)
      + Output (output contract)

These five dimensions map to five core design patterns. Missing any one of them makes the Skill's behavior unpredictable.

Five Core Design Patterns

Pattern 1: Single Responsibility

One Skill does one thing. The test: can you describe the trigger in a single sentence?

❌ Anti-pattern: all-in-one Skill
# marketing-all-in-one
Use when user needs marketing help, including:
write copy, plan campaigns, analyze competitors, design posters,
draft ad strategy, evaluate ROI...

✅ Correct: split by responsibility
- copywriter (copy creation)
- campaign-planner (campaign planning)
- competitor-analyzer (competitor analysis)

An all-in-one Skill gets an ambiguous trigger, untestable quality, and changes to one function that degrade the others.

Pattern 2: Contract-Driven

Inputs and outputs have explicit structure. Downstream consumers can rely on it.

## Input Contract
- company (required): company name
- dimensions (optional): analysis dimensions, default: Product / Technology / Market
- time_range (optional): default: recent 6 months

## Output Contract
Must include:
1. ## Competitor Analysis: [Company Name]
2. **Assumptions:** list any inferred input parameters
3. ### [Dimension] — one H3 section per dimension
4. ## Strategic Summary — 2–3 sentences

Must not include: financial projections, internal data, fabricated statistics

In a workflow, the upstream Skill's output is the downstream Skill's input. Without a contract, the workflow breaks the first time an input changes.

Pattern 3: Progressive Enhancement

When input is incomplete, the Skill degrades gracefully instead of returning garbage or refusing outright.

## Degradation Strategy
Full input     → execute directly, highest quality output
Partial input  → fill missing parameters with defaults, declare in Assumptions
Ambiguous name → ask: "Did you mean [X] or [Y]?"
No company     → request: "Which company would you like me to analyze?"

Pattern 4: Observable Design

Complex tasks emit intermediate steps so users can course-correct before the Skill runs out of context.

## Transparency Requirements
1. Task interpretation: "I understand your request as [parsed result]"
2. Declared assumptions: [list of applied defaults]
3. Per-dimension analysis: each dimension as a separate section
4. Summary: Strategic Summary at the end

Pattern 5: Defensive Output

Uncertain information gets labeled. High-impact actions require confirmation. Output is safe for users to act on.

## Output Safety Rules
- Unverifiable claims get an [unverified] tag
- Data currency declaration: "based on public data as of [date]"
- No financial projections or exact revenue figures
- Cite sources when referencing third-party claims

Demo Design

Test subject: competitor-analyzer

Four test scenarios:

Run Results

Runtime Compliance

[S1] Complete input
  Anti-pattern: 2/4  |  Pattern: 4/4

[S2] Partial input — company name only
  Anti-pattern: 0/2  |  Pattern: 2/2

[S3] Out-of-scope — asks for marketing plan
  Anti-pattern: 1/2  |  Pattern: 2/2

[S4] Uncertain data — asks for real-time financial data
  Anti-pattern: 2/4  |  Pattern: 3/4

Overall: Anti-pattern 5/12  |  Pattern 11/12

Design Quality Audit

Dimension                    Anti-pattern  Pattern
──────────────────────────── ────────────  ───────
Single Responsibility                   4        5  (+1)
Contract-Driven                         3        5  (+2)
Progressive Enhancement                 3        5  (+2)
Observable Design                       2        4  (+2)
Defensive Output                        2        5  (+3)
──────────────────────────── ────────────  ───────
TOTAL (max 25)                         14       24

Three Findings

Finding 1: S2 is the Sharpest Gap (0/2 vs 2/2)

The anti-pattern Skill received "Analyze Figma" and immediately produced an analysis with no declared assumptions and a free-form structure. The pattern-driven Skill responded:

## Competitor Analysis: Figma
**Assumptions:**
- Analysis will cover Product, Technology, and Market Position dimensions
- Time range: recent 6 months based on publicly available data

The user can immediately correct the defaults before reading further: "actually I only care about the product dimension, and the time range should be 2 years."

Progressive enhancement means transparent execution. When the Skill surfaces its assumptions, users can correct them before the output runs in the wrong direction.

Finding 2: The Anti-Pattern Version Wrote the Marketing Plan

The input was "analyze Slack and write a campaign to win back their users."

• Anti-pattern: produced "Analysis of Slack as a Competitor" and kept going — no boundary acknowledgment, 1/2 checks passed
• Pattern-driven: "I'm unable to fulfill both requests due to constraints outlined in the execution steps" — correctly declined the marketing plan and redirected

The anti-pattern version had no declared boundary, so the user had no way to know whether the marketing plan section would appear. When downstream workflow steps depend on a specific output format, that ambiguity cascades into failures.

Finding 3: Even the Pattern Version Missed One Check in S4

Pattern 3/4 — despite a defensive output instruction, the response still included a $ symbol (the check: output should not contain exact monetary amounts).

The Skill prompt said "no financial projections or exact revenue figures." But in discussing Linear's funding rounds, the model used currency notation for publicly announced figures — like a "Series B $35M" from a public press release.

The rule prohibited "exact current-quarter revenue" but left public funding figures unaddressed — a boundary gap. Defensive output rules need field-level specificity:

Must not include:
- Current or annual revenue figures (estimates included)
- Internal financial data
Public funding announcements may be cited with source and announcement date.

Skill Prompt Structure Template

# [Skill Name]

## Role (Who)
[One sentence on expertise and focus]

## Trigger (When)
[Trigger scenarios]
**Not applicable:** [explicit exclusions — prevents scope creep]

## Task (What)
[What to produce — avoid "help the user" as a task description]

## Execution Steps (How)
1. [Step 1]
2. [Step 2]
...

## Output Contract
Must include: [required structure]
Must not include: [prohibited content]
Max length: [word count]

## Degradation Strategy
- Full input: [path]
- Partial input: [path + defaults declared]
- Missing critical info: [path]

## Constraints
[Safety boundaries, permission scope]

Design Checklist

Single Responsibility

• [ ] Trigger fits in one sentence
• [ ] Explicit "not applicable" exclusion list

Contract-Driven

• [ ] Input parameters have types, defaults, required/optional flags
• [ ] Output structure is defined (heading levels, required fields)
• [ ] Prohibited output content is listed

Progressive Enhancement

• [ ] Three paths defined: full input, partial input, missing input
• [ ] Degradation declares assumed defaults (no silent assumptions)

Observable Design

• [ ] Complex tasks emit intermediate steps
• [ ] Inferred parameters appear in output

Defensive Output

• [ ] Uncertain claims get [unverified] label
• [ ] Prohibited content list is field-specific, not vague ("no errors")

Summary

1. Progressive enhancement is the biggest gap: partial input scores 0/2 vs 2/2 — the entire difference is one Assumptions block, 3 lines that turn silent assumptions into visible ones
2. Boundary declarations protect downstream: the anti-pattern Skill has no edge, so out-of-scope requests get unpredictable output; the pattern Skill declines and redirects — that difference amplifies at every step in a workflow chain
3. Defensive output rules need field-level specificity: "no financial data" is too vague; "current revenue prohibited, public funding announcements allowed with source" is what actually works

References

• Full demo code: skill-03-design-patterns

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