/ice-score

name: ice-score
description: "Use to prioritize solutions or opportunities using ICE scoring with evidence-backed confidence."
metadata:
  instruction_budget: "35"
  framework_dependency: "mycelium"
  framework_dependency_note: "This skill is designed to run within the Mycelium framework (https://github.com/haabe/mycelium). Standalone use will skip the canvas state, theory gates, and harness behavior the skill assumes. Install: /plugin install mycelium@haabe-mycelium."

ICE Score Skill

ICE scoring as Itamar Gilad defines it: Impact x Confidence x Ease, each 0-10, with Confidence taken from his Confidence Meter.

Preflight: Read target canvas file(s) before any Write/Edit

**Hard rule.** Before issuing `Write` or `Edit` against any `.claude/canvas/*.yml`, use the **Read tool** on that file in this session. Claude Code's Read-before-Write check requires the `Read` tool specifically — `cat`/`head`/`grep` via Bash do NOT satisfy it.

**Edit vs Write — different cost profiles** (verified 2026-05-14):

• **`Edit`** (exact-string replacement): `Read` with `limit: 1` satisfies the check at ~50 tokens. State-tracking is per-file, not per-byte — subsequent `Edit` calls work anywhere in the file. Use this for partial updates against large canvas files (e.g., `purpose.yml` at 800+ lines).
• **`Write`** (full replacement): do a **full Read** first. Write obliterates the file; you should see what you're about to replace. The `limit:1` shortcut is *not* appropriate here.

**ID-bearing entries — scan the ID space before assigning** (added 2026-05-15, v0.23.19): When adding a new component, opportunity, solution, or any other ID-bearing entry to a canvas file, run a Bash grep first to confirm the next ID in your prefix sequence is actually free:

grep -o "<prefix>-[0-9][0-9]*" .claude/canvas/<file>.yml | sort -u -t- -k2 -n | tail -3

Replace `<prefix>` with the canvas's ID prefix (`comp` for landscape, `opp` for opportunities, `sol` for solutions, `ht` for human-tasks, etc.). Then pick the next free integer, **matching the zero-padding already used in that file**. The sort is NUMERIC (`-t- -k2 -n`) rather than lexical, and that is not pedantry: a plain `sort -u` orders `ht-1` after `ht-080`, so on a canvas with inconsistent padding it reports the wrong maximum and the next ID collides. Verified on the dogfood repo 2026-08-13, where lexical sort returned `ht-1` as the highest human-task ID against an actual `ht-080`. `grep -o` is also deliberate: it matches IDs wherever they appear, including cross-references and prose, so an ID that was promised somewhere but not yet defined is not handed out twice. `validate_canvas.py` has a per-file duplicate-ID check (it reports `duplicate id '<id>'`) that catches the failure on CI, but a duplicate can persist in the working tree for days if CI isn't run between edit and discovery; that happened on 2026-05-15, when a duplicate ID was created in `landscape.yml`.

Original failure mode: anti-pattern #7 instance #5, 2026-05-09 — agent conflated Bash `head` with the Read tool, lost ~14k tokens to a Write-fail → remedial-full-Read → re-Write loop. The `limit:1` discipline (graduated 2026-05-14, v0.23.18) prevents the second-order cost where the agent *correctly* follows the rule but full-Reads every time. The ID-scan discipline (graduated 2026-05-15, v0.23.19) prevents the related class where the agent reads enough of the file to satisfy the Edit check but not enough to see existing ID assignments — kin to anti-pattern #8 (Stale State Read).

If this skill writes to multiple canvas files, register each one first (limit:1 for Edit-only paths; full Read for Write paths) AND ID-scan any prefix you intend to assign.

See `${CLAUDE_PLUGIN_ROOT}/engine/agent-operating-contract.md` *Canvas writes — Read before Write* for the canonical rule.

Which ICE this is

> **Why this note exists.** ICE has two versions in the literature, and until 0.319.0 this skill > matched neither. It averaged the three numbers, which is Ellis's arithmetic, while describing > Gilad's Confidence Meter with values and bands that are in no version of his meter. The > maintainer chose Gilad's version on 2026-10-11, after a read of both authors' own texts. If you > scored with this skill before 0.319.0, read the last paragraph of this section.

**Ellis's ICE** ranks a growth team's backlog of experiments. Sean Ellis invented it: *"At GrowthHackers, Sean developed the ICE score system"* (Ellis & Brown, *Hacking Growth*, ch. 4). The person who submits an idea rates it *"on a ten-point scale, across each of the following three criteria"*, and *"Then those ratings are averaged to provide an aggregate score for each idea"* (same chapter). His Ease is the cost of the test, not of the finished thing: *"Ease is the measure of the time and resources needed to run the experiment."*

**Gilad's ICE** scores product ideas in an idea bank. He credits Ellis as the inventor. His version differs from Ellis's in four ways: the scale starts at 0, Ease is the effort to build the idea in full, Confidence is worked out from evidence with his Confidence Meter, and the three are multiplied. The score is the product: *"With ICE, each idea is assigned three numeric attributes: Impact, Confidence, and Ease, each in the range 0–10. A fourth value holds the ICE score, which is simply the three values multiplied together"* (Gilad, *Evidence-Guided*, ch. 3). His ebook also allows the average: *"We multiply (or average) Impact, Confidence and Ease to get the ICE score."* (*ICE Done Right*, p. 4). Every worked example of his that was read multiplies, and in the texts read he does not argue for one operation over the other.

**Mycelium uses Gilad's, multiplied.** What is scored here is a product idea (an OST solution leaf, a GIST idea), and the Confidence comes from his meter. The reasoning for the product is Mycelium's own and is not a statement of his: the meter's values are small and far apart (0.01 for a conviction