The Kirra Formula skill teaches Claude to write and check Kirra fx: formulas — across all
three formula engines — and to do so from the Kirra source rather than guesswork. Install it once
and ask for formulas in plain English; Claude identifies the right engine, picks the correct
prefix and scaling flag, and hand-traces the result before giving it to you.
This page covers what the skill does, how to install it on each Claude surface, and how to verify it loaded.
Human-readable references (no Claude required): Formula Engine hub, Deck Builder Formula Guide, Print Formula Reference, Blast Group Formulas.
Kirra has three separate formula engines that all use the fx: prefix but are not
interchangeable. Using the right syntax in the wrong field is the most common formula error. The
skill’s first job is to route each request to the correct engine, then use only that engine’s
variables and functions.
| Engine | Where the formula lives | Examples it handles |
|---|---|---|
| Charging | Deck length, deck mass, or primer depth (Deck Builder / chargeConfigs.csv) |
fx:chargeBase - 0.3, fx:Math.max(1.6, sdobStem(1.5,"ANFO")), ppvKG(...) |
| Print template | A cell in an XLSX/PDF print template | fx:round(sum(holeLength[i]),1), groupTable(...), mapView(v) |
| Blast group | The Formula field of the Assign Group dialog (hole selection) | fx:holeLength < 2, fx:holeType == "Production" && burden >= 4.5 |
It also knows the limits: a formula is one expression evaluated once per deck — no loops or goal-seek — and powder factor, burden, spacing, and volume are not charging-formula variables, so a PF-driven deck formula isn’t possible today. The skill says so plainly instead of inventing one.
See also: Formula Engine and Deck Builder Formula Guide & Examples for the full variable and function reference the skill is built from.
Download from this docs folder:
kirra-formula/ — plain folder with SKILL.md and references/ (for Claude Code; unzip the zip or copy from the Kirra distribution)Both contain the same thing; the surface decides which you use.
Recommended for most users.
kirra-formula.zip.Requires a plan with Skills and code execution enabled (Pro, Max, Team, or Enterprise). If you don’t see a Skills section, the feature may be off for your plan or organisation.
Claude Code reads skills from a folder — no upload.
Copy the kirra-formula/ folder into your personal skills directory:
mkdir -p ~/.claude/skills
cp -r kirra-formula ~/.claude/skills/
The result must be ~/.claude/skills/kirra-formula/SKILL.md — not nested one level too deep.
~/.claude/skills/ is brand new, restart Code so it
begins watching the directory.)/skills to confirm kirra-formula is listed.To ship the skill with the Kirra repo for your team, place the folder in the project’s
.claude/skills/ instead. Project skills override personal ones of the same name.
The Chrome extension is a browser-automation agent and has no Skills installer at present. Two options:
SKILL.md (plus
references/charging.md if your question is about charge decks), then ask. This works as a
one-off but must be re-pasted each session — it’s a prompt, not an installed skill.Claude for Chrome is in beta. If a Skills option appears in the extension later, use it in preference to the paste method.
Ask any of these and check Claude names the engine, picks the prefix/flag, and shows a worked trace:
| Ask | Expected engine and answer |
|---|---|
| “Total drill metres for my report.” | Print template — fx:round(sum(holeLength[i]),1) |
| “Primer 0.3 m above the deepest charge.” | Charging — fx:chargeBase - 0.3 |
| “Group all holes shorter than 2 m.” | Blast group — fx:holeLength < 2 |
If Claude puts a report function into a charge deck (or vice versa), the skill isn’t loaded — recheck the install steps for your surface.
Kirra Licence v1.0 — Kirra Design is free for mining, quarrying, construction, and research use. Commercial software integration requires written permission from Brent Buffham. See About for details.