# Td Author > Authors and audits Tool Definition (TD) documents and the SKILL.md paired with them — keeps the governance and reasoning (TD) separate from the operating instructions (SKILL.md), and enforces the document structure and version-history discipline. Use whenever a new tool is being created, a TD is being written or updated, a skill is being renamed or repackaged, an old tool version is being archived, or someone asks to review a tool's documentation for drift. Also use proactively on noticing a SKILL.md accumulating dated narration or changelog-style history, or a TD whose body has started describing what changed rather than how the tool works — that content belongs in the version history, and catching it early is this skill's job. - Skill: `esp1ngard4/td-author` (Agent Skill) - Install (CLI): `npx skillmds@latest add esp1ngard4/td-author` - Raw SKILL.md: https://api.skillmd.com/api/skills/esp1ngard4/td-author/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Docs & Writing - Author: Esp1ngard4 (https://skillmd.com/u/esp1ngard4) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/esp1ngard4/td-author --- # Tool Definition Author Every tool has a **TD** — the document that says why it exists and how it is governed. Tools that are automated also have a **SKILL.md**. This skill owns the first and polices the boundary between them. The reasoning behind these rules is in the method: [governance docs](../../../method/02-governance-docs.md), [source of truth](../../../method/03-source-of-truth.md), [versioning discipline](../../../method/05-versioning-discipline.md). This file is the procedure. **The boundary with `tsp-manager`: this skill owns the document, that one owns the register row.** When a tool gains or loses a TD, write it here and flip `Doc Aux` there. Neither does the other's write. ## The core split: TD vs SKILL.md - **TD — the "why".** Purpose, components, governance, conventions, relationships to other tools, maintenance, version history. Dates and decisions live here. - **SKILL.md — the "what and how".** Operating instructions, loaded into context every time the skill triggers. Durable rules and their *timeless* rationale belong here. Dated narration and "as of " framing do not: every sentence of backstory is a permanent tax on every future invocation, whether or not that invocation needs it. **The test for a borderline sentence:** would removing it change what the model does on the next run? If yes, and the reasoning is timeless, it belongs in SKILL.md. If it explains *how a rule came to be* rather than what to do, it belongs in the TD. ## History belongs in the version history, not the body The split above has a second edge inside the TD itself, and it is easier to cross because the TD *is* where history belongs — just not anywhere in it. - **Design rationale** — why the tool is shaped the way it is — belongs in the body, and is timeless. *"Two parent columns, because an artifact that is both scanned and filed has two real locations."* - **Change narration** — what this version altered, replaced, merged or migrated — belongs only in the version history table. *"This document replaces the 2020 one and merges in the tool that had been running separately."* **The test:** would the sentence still be true if the previous version had never existed? If yes it is rationale and stays. If it only makes sense by reference to what came before, it is history and moves to the table. The failure mode is writing the TD in the same session as the change it documents, when the migration narrative is still front of mind. Before declaring a TD done, sweep the body for `replaces`, `previously`, `used to`, `earlier`, `no longer` and bare years. Each hit is either a genuine open item, a provenance note, or a line that belongs in the version history. ## TD structure Mirror this order. Not every tool needs every section, but check each one deliberately rather than skipping silently. 1. **Purpose** — what the tool is for. 2. **Components** — a table: component, provenance, location, purpose. **State which copy is the source of truth, in words.** Get this wrong and everything built on top inherits the error, because each new document copies the assertion from the last without anyone re-checking. A components table that has never been verified against the disk is a rumour. 3. **What the skill covers (and this document doesn't repeat)** — a pointer, so the TD does not duplicate content that will drift. 4. **Naming conventions** — files, identifiers, folders. 5. **Relationship to other tools** — how data flows to and from siblings, including deliberate boundaries and what stays manual. 6. **Maintenance** — regular use, plus periodic tasks. 7. **Open items** — what is known-wrong or undecided. A TD with no open items is usually a TD nobody has read critically. 8. **Version history** — the table. All the dated narration that must not live in SKILL.md goes here. ## Version history: order and length **Newest first.** New entries at the top, the original at the bottom. This sounds too obvious to state, and it isn't: entries get inserted one at a time, and a table originally written oldest-first ends up sorted in two directions at once. **Verify the whole column after editing, not just the row you added.** **Keep the three most recent.** A TD is read to understand the tool as it is now; an unbounded table buries that under superseded reasoning. **Trimming never deletes history.** Before trimming, copy the whole TD to `PreviousV/TD. - v (YYYY-MM-DD).md`. The full history rides along inside that snapshot, so there is nothing extra to maintain. Leave a line under the trimmed table pointing at the most recent snapshot. Deliberately *not* the approach: a separate curated history document. It is a second file to keep in sync, the rule is easy to forget, and when it is forgotten it rots silently — whereas a snapshot is worth taking before a structural edit anyway. ## Process ### A new tool 1. Claim the ID through `tsp-manager` — do not invent one. 2. Build the tool. Write the TD **after** the design has actually been exercised; writing it earlier just means rewriting it once the design shifts. 3. Write the TD from [`templates/TD-template.md`](../../../templates/TD-template.md). 4. Set `Doc Aux` and the `Skill` column through `tsp-manager`. 5. Final pass on SKILL.md for the split above — easy to violate in the satisfaction of having just made something work. ### Updating a tool 1. Change the tool first. 2. Add a version-history entry saying what changed **and why**. 3. Sweep SKILL.md for narration describing *this specific change* rather than the durable rule it produced. Move it to the TD. 4. Sweep the TD body with the grep list above. ### Auditing a pair 1. Read both documents in full. 2. **Check the components table against what is actually on disk.** Verify; do not trust the document's own prior claims. 3. Check SKILL.md for dated or historical language. 4. Check that the "what the skill covers" pointer has not itself drifted into duplicating the real SKILL.md. 5. Report findings. Do not silently fix beyond what was asked — a full audit turns up more than the request. ## Verification discipline **Never mark a documentation change done without reopening the file and confirming the edit landed.** This is not paranoia: a register elsewhere in this collection logged several schema changes as complete that a later inspection found had never been written to the live files. The same applies to anything with a current-versus-stale split — a renamed skill's old package, a generated view built from data that has since changed. ## Relationship to other skills - **`tsp-manager`** — the other half of this same tool. It owns the register row; this owns the document. - **A skill scaffolder** (Anthropic's `skill-creator`, or equivalent) covers the generic mechanics of building and evaluating a skill. This skill layers the governance on top — use both when creating a tool, not one instead of the other. It is externally supplied, so it is referenced rather than vendored here; see [owned vs. used](../../../method/04-owned-vs-used.md).