Book to skill

Contract

Field	Bound contract
Trigger	The user names one book, course, paper, or comparable single source document and asks to distill it into a reusable skill.
Authority	Reversible local write. Writes only the chosen target skill directory (SKILL.md and optional references/). Rollback is deleting that directory. No source file is mutated or copied wholesale.
Side effect	Creates files under the chosen target directory only; never copies the source document into the skill.
Done	A SKILL.md that parses as YAML, carries an attribution line, passes four validation checks, and routes correctly on at least two positive and two negative probe prompts.

Inputs

• The named source document, accessible as a file the agent can open. A document the agent cannot open stops the run.
• Optional: a write target directory, defaulting to .claude/skills/<name>/.
• A folder of multiple sources is out of scope; that belongs to corpus mapping, not this skill.

Procedure

1. Read the source. List its chapters, top-level headings, or sections, whichever structure the document provides. Show one line per unit with its heading slug where one exists. Done when: an inventory covering every top-level unit is shown.
2. Classify. Ask whether three or more ordered actions can be named, each with a checkable done-state. Three or more is procedure (a sequence the agent can follow). Fewer is reference (distinctions and rules consulted on demand). If both are present, use a procedure spine with judgment material in references/. Done when: the classification is stated with the three actions named, or with the statement that fewer than three exist.
3. Extract into four buckets. Sort what you read into coined terms and leading words; constraints and prohibitions; procedures with their completion criteria; and deep material destined for references/. Done when: every inventoried unit has contributed to a bucket or is marked out of scope for the skill.
4. Name it. Kebab-case matching ^[a-z0-9]+(-[a-z0-9]+)*$, at most 64 characters, identical to the directory name. Done when: the name matches the directory to be written to.
5. Write the frontmatter. description at most 1024 characters, front-loaded, one trigger per genuinely distinct branch, phrased positively. Redirect rather than forbid: "for X, use skill Z" rather than "do not use for X". Done when: the description parses as single-quoted YAML and is within the limit.
6. Write the body in the shape its classification selects. Include one attribution line naming title, author, and year. Paraphrase throughout; quote only a coined term or named law where the exact phrasing is the idea. The two shapes:
   • Procedure shape:

     # {Skill name}
     {One-paragraph attribution: title, author, year.}
     ## When to use
     {One trigger per branch, positively phrased.}
     ## Steps
     1. {Action} — done when {checkable condition}
     2. {Action} — done when {checkable condition}
     ## Rules
     - {Constraint or guardrail}
     

   • Reference shape:

     # {Skill name}
     {One-paragraph attribution: title, author, year.}
     ## When to use
     {One trigger per branch, positively phrased.}
     ## Reference
     {Definitions, distinctions, or judgment material consulted on demand. No ordered steps.}
     ## Rules
     - {Constraint or guardrail}
     

   • A source with both gets the procedure shape with judgment material in references/. Every step ends on a checkable done condition; a reference shape carries no steps. The frontmatter description is the only place the trigger is worded for dispatch; the body restates the when as prose but does not re-word the trigger for dispatch. Done when: the body follows its shape and carries the attribution.
7. Disclose. Material only some branches reach moves to references/<topic>.md, linked one level deep from the body. Keep the body under 500 lines. Done when: branch-specific material lives behind a pointer and the body line count is under the cap.
8. Validate. Check four conditions: name equals the directory name; the frontmatter parses as YAML; description is within 1024 characters; every relative link resolves on disk. Run yaml.safe_load on the frontmatter and test -f on each link target. Done when: all four pass.
9. Probe and place. Author three to five probe prompts — at least two that must fire the skill and at least two out-of-scope prompts that must not — and run each in a subagent. Adjust the description until every probe lands correctly. Then ask for the write target, defaulting to .claude/skills/<name>/, and re-run step 8 there. Done when: probe results are reported and the checks are green at the target.

One skill per run; another source is another run. Paraphrase the source; do not paste it. The skill, not the book, is the source of truth when the skill runs — keep it runnable without the source in context.

Failure and recovery

• Source unopenable. A file the agent cannot open stops the run; name the file. This skill owns no converter and does not invent content for a source it cannot read.
• Fewer than three ordered actions. Not a failure — classify as reference and proceed with the reference shape.
• Validation check fails. Fix the offending field or link and re-run step 8. Do not claim done while any check is red.
• Probe lands wrong. Adjust the description and re-probe. Never mark done with a misrouting probe; a wrong negative probe is as blocking as a wrong positive one.
• Partial result. If the run stops mid-procedure, the written files are incomplete. Either complete the procedure or delete the target directory as rollback. Do not leave a half-written skill that parses as valid.
• Rollback. Delete the target skill directory. No artifact outside that directory is touched, so deletion is a complete recovery.

Output

A self-contained SKILL.md (and optional references/<topic>.md) under the chosen target directory, carrying an attribution line and passing all four validation checks and the probe set — the report states the classification, chosen name, target path, validation results, and probe results (positive and negative).