What is building-a-spell?

A guided builder that turns a repeated task into a reusable spell, meaning a saved set of instructions that can be triggered again.

Use it to systematize recurring research, operations, writing, or development work and save the resulting SKILL.md file.

It captures a process once so the same approach can be followed consistently in future sessions.

building-a-spell — Skill for Claude Code by redhuntlabs: A guided builder that turns a repeated task into…

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/redhuntlabs/wizard/building-a-spell

Any agent

npx skills add redhuntlabs/wizard --skill building-a-spell

Clone the repo

git clone --depth 1 https://github.com/redhuntlabs/wizard

Made for: Claude Code.

Or install wizard, the plugin that ships this one along with the rest of its 37 skills, 6 commands, 1 agent, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/redhuntlabs/wizard/building-a-spell.svg)](https://agentmods.dev/skills/redhuntlabs/wizard/building-a-spell)

Your own site

<a href="https://agentmods.dev/skills/redhuntlabs/wizard/building-a-spell"><img src="https://agentmods.dev/badge/skills/redhuntlabs/wizard/building-a-spell.svg" alt="Measured on agentmods" height="20"></a>

Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,306 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00037	$0.02306
Opus 5	$0.00018	$0.01153
Sonnet 5	$0.00007	$0.00461
Haiku 4.5	$0.00004	$0.00231

Measured 6d ago against content hash 06a5ac2e27ca, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

building-a-spell scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/building-a-spell/SKILL.md · 221 lines

How it starts

The opening of the file, as written. The whole thing — 221 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Building a Spell

What this does

Interviews the user about a task they do repeatedly, then writes a spell file (a SKILL.md) that captures it. Future sessions auto-invoke that spell whenever the trigger matches.

This skill is the meta-builder. It calls other skills (intuitive-interviewing, kind-specific builders, pressure-testing-a-spell) and dispatches the spell-tester subagent.

When to use

User describes a task they do over and over and asks to capture it
User says "build a workflow / skill / spell for X"
User shows you a process and says "I want this systematized"
User wants the AI to behave the same way every time they hit a certain trigger

What you bring (Inputs)

A description of the task (one or two sentences is enough)
Your domain (research, ops, writing, dev, etc.) — inferred if not stated
Any constraints (time budget, tools available, style preferences)

What you get (Output)

A new spell file at $WIZARD_HOME/<category>/<name>/SKILL.md, validated and tested.

How it works (Steps)

This is a workflow chain. The stages below are the master flow.

Stages

Stage -1: Inference prelude (conditional)

Skip this stage entirely if no transcript was supplied (the default /build-spell flow).

If invocation came with --from-transcript <path> OR was routed through /capture-this-chat, the input includes a transcript blob plus provenance.

In that case:

Invoke inferring-a-spell-from-examples (passes the transcript + provenance).
The inference skill produces either:
- A BUILDABLE outcome → context dictionary + draft SKILL.md. Resume at Stage 2 (kind-route) with kind already set. Skip Stage 0 and Stage 1 entirely.
- A TOO-THIN or TOO-BROAD outcome → halt with the inference skill's user-facing message. Do not enter Stages 0–4.
- A user choice of "Re-do as interview" (bail) → resume at Stage 1 with the inferred fields as pre-filled defaults. Stage 1's batch-confirm still runs; user can accept-with-Enter or correct.

Read the full file on GitHub · 221 lines

Files

What ships with it

16 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

6d ago First seen · 221 lines · 37 tokens per session scan A 06a5ac2e27ca

Subscribe to this mod's changes

building-a-spell is a skill published in the GitHub repository redhuntlabs/wizard (9 stars, last pushed 4mo ago), licensed MIT. It adds 37 tokens to every session and 2,306 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Building agents ai-agents ai-skills ai-tools ai-workflow automation claude-code

building-a-spell