How do I install the Fable Engine skill?

Run npx get-skill add cleanexpo/fable-engine in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Fable Engine safe to use?

SkillMD's automated safety review verdict for this skill is PASS. Independent scanners report: SkillSpector: PASS, Skill Scanner: PASS. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Fable Engine?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Fable Engine free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Fable Engine?

cleanexpo (@cleanexpo) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Fable Engine by cleanexpo — Agent Skill

Name: Fable Engine
Author: cleanexpo

Fable Engine

Turn a plain-English vision or task into a verified, build-ready spec before any code. Locks the finish line, researches across channels, enforces the Evidence Standard, stops at the human gate. Adopted from CleanExpo/Fabel-Prompt-Engineer for the Synthex build process.

cleanexpo Updated Sep 17, 2026

File contents

Fable Engine (Synthex build process)

Input: a vague idea or a non-trivial change in plain English. Output: a precise, sourced, build-ready spec. You propose; the human decides. Pairs with .claude/rules/fabel-evidence-standard.md and .claude/FABEL_PLAYBOOK.md.

Use it for: a new feature, a workstream/elevation wave, a risky refactor, or any multi-agent fan-out. Skip it for: a one-line fix or a conversational answer (Fabel directive 1 — act when you have enough info).

Operating loop

1. Lock the finish line

Restate the task as one testable sentence: "Done when ___." If several finish lines are plausible, pick the most likely, state it, list the rejected ones. Emit: [STATUS] finish-line: locked — <one sentence>

2. Research channels (emit started/done per channel)

Source channel — read the actual Synthex code + .claude/ rules that constrain or accelerate the change. Docs are stale; the source is truth.
Prior-work channel — search merged PRs, .claude/scratchpad, memories, and open PRs for decisions and existing patterns (e.g. defineRoute, getEffectiveOrganizationId, the deploy-pipeline gotchas).
Web channel — for external facts (API shapes, prices, library versions) use Context7 / web; every web finding carries its source URL. No web access → mark skipped, downgrade affected claims to [UNCONFIRMED].

3. Filter through the Evidence Standard

Every finding and spec claim is tagged [VERIFIED] / [INFERENCE] / [UNCONFIRMED] per fabel-evidence-standard.md. An untagged claim is a defect.

4. Synthesize, ask only what you can't infer

Draft the spec. Infer-and-tag rather than ask. Where info is genuinely missing, list ≤5 concrete, answerable questions.

5. Board critique (high-stakes or on request)

Run boardroom / ask-the-board on the draft; append the combined critique as a lens. Label it [INFERENCE] — persona synthesis, not fact. It feeds the gate, never bypasses it.

6. Approval gate

Present the spec and stop. Nothing builds until the human approves. For the agent fleet: the spec is the contract each subagent is dispatched against, and the prod-deploy gate remains the founder's call. Emit: [STATUS] gate: awaiting approval

Spec output format

Finish line — the locked "done when" sentence.
Decision up front — recommended path in one paragraph.
Goals & non-goals — non-goals required.
Approach — plain language first.
Phased plan — smallest phase first; each phase has a definition of done; no later phase before the earlier DoD is met. For a fleet wave: the disjoint agent lanes + their file boundaries.
Data model — if it stores anything (respect the Synthex migration rules: apply_migration only, never prisma db push).
Security & cost guardrails — secrets, org-scoping, spend; structural not advisory.
Risk & assumption register — every [UNCONFIRMED] lands here.
Open questions — the ≤5 from step 4, if any.
Verification plan — the exact commands that will prove "done" (build:vercel, npm test -- --coverage, the integration gauntlet). Per Fabel directive 5, a claim isn't done until its tool result says so.

Status grammar

[STATUS] <subject>: <state>[ — detail] — subjects: finish-line, channel:source, channel:prior-work, channel:web, synthesis, board, gate.

---name: fable-enginedescription: Turn a plain-English vision or task into a verified, build-ready spec before any code. Locks the finish line, researches across channels, enforces the Evidence Standard, stops at the human gate. Adopted from CleanExpo/Fabel-Prompt-Engineer for the Synthex build process.---# Fable Engine (Synthex build process)Input: a vague idea or a non-trivial change in plain English. Output: a precise,sourced, build-ready spec. You propose; the human decides. Pairs with`.claude/rules/fabel-evidence-standard.md` and `.claude/FABEL_PLAYBOOK.md`.Use it for: a new feature, a workstream/elevation wave, a risky refactor, or anymulti-agent fan-out. Skip it for: a one-line fix or a conversational answer(Fabel directive 1 — act when you have enough info).## Operating loop### 1. Lock the finish lineRestate the task as one testable sentence: _"Done when \_\_\_."_ If several finishlines are plausible, pick the most likely, state it, list the rejected ones.Emit: `[STATUS] finish-line: locked — <one sentence>`### 2. Research channels (emit started/done per channel)- **Source channel** — read the actual Synthex code + `.claude/` rules that constrain or accelerate the change. Docs are stale; the source is truth.- **Prior-work channel** — search merged PRs, `.claude/scratchpad`, memories, and open PRs for decisions and existing patterns (e.g. `defineRoute`, `getEffectiveOrganizationId`, the deploy-pipeline gotchas).- **Web channel** — for external facts (API shapes, prices, library versions) use Context7 / web; every web finding carries its source URL. No web access → mark skipped, downgrade affected claims to `[UNCONFIRMED]`.### 3. Filter through the Evidence StandardEvery finding and spec claim is tagged `[VERIFIED]` / `[INFERENCE]` /`[UNCONFIRMED]` per `fabel-evidence-standard.md`. An untagged claim is a defect.### 4. Synthesize, ask only what you can't inferDraft the spec. Infer-and-tag rather than ask. Where info is genuinely missing,list ≤5 concrete, answerable questions.### 5. Board critique (high-stakes or on request)Run `boardroom` / `ask-the-board` on the draft; append the combined critique asa lens. Label it `[INFERENCE] — persona synthesis, not fact`. It feeds the gate,never bypasses it.### 6. Approval gatePresent the spec and stop. Nothing builds until the human approves. For theagent fleet: the spec is the contract each subagent is dispatched against, andthe prod-deploy gate remains the founder's call.Emit: `[STATUS] gate: awaiting approval`## Spec output format1. **Finish line** — the locked "done when" sentence.2. **Decision up front** — recommended path in one paragraph.3. **Goals & non-goals** — non-goals required.4. **Approach** — plain language first.5. **Phased plan** — smallest phase first; each phase has a definition of done; no later phase before the earlier DoD is met. For a fleet wave: the disjoint agent lanes + their file boundaries.6. **Data model** — if it stores anything (respect the Synthex migration rules: `apply_migration` only, never `prisma db push`).7. **Security & cost guardrails** — secrets, org-scoping, spend; structural not advisory.8. **Risk & assumption register** — every `[UNCONFIRMED]` lands here.9. **Open questions** — the ≤5 from step 4, if any.10. **Verification plan** — the exact commands that will prove "done" (`build:vercel`, `npm test -- --coverage`, the integration gauntlet). Per Fabel directive 5, a claim isn't done until its tool result says so.## Status grammar`[STATUS] <subject>: <state>[ — detail]` — subjects: `finish-line`,`channel:source`, `channel:prior-work`, `channel:web`, `synthesis`, `board`,`gate`.

Frequently asked questions