ETC - Expand the Etcetera

Input: $ARGUMENTS

Core Principles

1. “Etc” is a claim of pattern continuation. When someone writes “A, B, C, etc.” they’re asserting that a pattern exists and continues predictably. But the pattern they intend is often not the pattern that’s obvious. “Red, blue, green, etc.” — is the pattern primary colors? Colors of the rainbow? Colors in their CSS file? The continuation rule must be inferred, not assumed.

2. The list head constrains the list tail. The items explicitly stated define the category, granularity, and scope of what follows. “Apples, oranges, etc.” means fruits — not “apples, oranges, trucks, democracy.” The head establishes a membership test that every expanded item must pass.

3. Omission is often strategic. People don’t write “etc” randomly. They include the items that seemed most important, representative, or top-of-mind, and omit the rest. The omitted items are often less obvious, less prototypical, or less favored — which is exactly why expanding them matters.

4. Lists have finite completions. Every “etc” has a point where the category is exhausted or continuing adds no value. The skill must define a stopping rule, not just keep generating. An unbounded expansion is as useless as the original “etc.”

5. Multiple valid continuations exist. “Dogs, cats, etc.” could expand to {hamsters, fish, birds} (common pets), {wolves, lions, tigers} (related wild animals), or {horses, cows, pigs} (domesticated animals). The continuation depends on the RULE, and the rule depends on CONTEXT. Surface the rule explicitly.

Phase 1: Head Extraction

[E1] RAW_INPUT: [the full statement containing "etc" or equivalent, quoted]
[E2] LIST_HEAD: [the explicitly stated items, in order]
[E3] HEAD_COUNT: [how many items were explicit]
[E4] TAIL_MARKER: [what indicated continuation — "etc", "and so on", "...", ellipsis, "among others"]
[E5] CONTEXT: [surrounding text or situation that constrains interpretation]

Phase 2: Rule Inference

What pattern connects the explicit items?

[E6] CANDIDATE_RULES: [list 2-3 possible continuation rules]
  RULE_1: [pattern] — FITS_HEAD: [yes/partial] — EVIDENCE: [what supports this]
  RULE_2: [pattern] — FITS_HEAD: [yes/partial] — EVIDENCE: [what supports this]
  RULE_3: [pattern] — FITS_HEAD: [yes/partial] — EVIDENCE: [what supports this]

[E7] SELECTED_RULE: [the most likely continuation rule]
  CONFIDENCE: [high | medium | low]
  WHY_THIS_RULE: [what makes this interpretation strongest]
  MEMBERSHIP_TEST: [how to determine if a candidate item belongs — the explicit inclusion criterion]

Rule Inference Strategies

If confidence is low, present multiple expansions under different rules.

Phase 3: Expansion

Enumerate the omitted items:

[E-N] ITEM: [expanded item]
  WHY_INCLUDED: [how it satisfies the membership test]
  CONFIDENCE: [high | medium | low — how certain this belongs]
  WHY_OMITTED: [why the author likely didn't include it explicitly — less prototypical, less common, less important, or assumed obvious]

Expansion Quality Rules

• Every item must pass the membership test from Phase 2
• Maintain the same granularity as the head items — if the head has “Python, Java,” don’t expand with “programming” or “Python 3.11”
• Order by relevance — most likely omissions first, edge cases last
• Flag edge cases — items that might or might not belong, depending on interpretation

Phase 4: Completeness

Define when to stop:

[E-N] STOP_RULE: [the criterion for completeness]
  TYPE: [exhaustive | representative | threshold | diminishing]
  TOTAL_ITEMS: [head + expanded = N]
  REMAINING: [items deliberately excluded and why]

Stopping Criteria

Phase 5: Output

EXPANDED LIST
=============

ORIGINAL: [quoted input with "etc"]
RULE: [the continuation pattern]
CONFIDENCE: [level]

EXPLICIT (from author):
  1. [item]
  2. [item]
  3. [item]

EXPANDED (inferred):
  4. [item] — CONFIDENCE: [level]
  5. [item] — CONFIDENCE: [level]
  6. [item] — CONFIDENCE: [level]
  ...

EDGE CASES (might belong):
  - [item] — DEPENDS_ON: [what interpretation]

STOP: [completeness criterion] — TOTAL: [N items]

ALTERNATIVE RULE: [if a different continuation rule exists]
  WOULD PRODUCE: [different expansion under that rule]

READY FOR:
- /se [category] — to systematically enumerate instead of inferring
- /mv — to validate the expanded list is MECE
- /aso — to expand "and so on" patterns (related skill)

Failure Modes

Depth Scaling

Default: 2x. These are floors.

Pre-Completion Checklist

• List head extracted with all explicit items
• Continuation rule inferred explicitly (not assumed)
• Membership test defined
• Multiple candidate rules considered
• Expanded items all pass the membership test
• Granularity matches the head items
• Stop rule defined and applied
• Edge cases flagged where appropriate
• At least one alternative interpretation noted (at 2x+)

Integration

• Use from: encountering “etc”, “and so on”, ”…”, incomplete lists, vague enumerations
• Routes to: /se (systematic enumeration for thorough coverage), /mv (validate list structure)
• Complementary: /aso (handles “and so on” patterns — related but distinct trigger)
• Differs from /se: se generates lists from scratch; etc expands an existing partial list
• Differs from /aso: aso focuses on continuation patterns; etc focuses on category membership and completion
• Differs from /list: list builds lists with quality criteria; etc expands existing compressed lists