copy

A set of writing rules for user-facing text, including tone, banned phrases, terminology, and editing checks.

In plain words
What is it for?
Use it when editing text in the project’s web pages or documentation. It also defines which prose should not be changed without permission.
Why use it?
It keeps product copy consistent and removes filler, exaggerated language, and terminology mistakes.

Cursor rule for Cursor

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 rules/heavyblotto/caelus/copy
Clone the repo
git clone --depth 1 https://github.com/heavyblotto/caelus

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 365 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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00365
Opus 5 $0.00000 $0.00182
Sonnet 5 $0.00000 $0.00073
Haiku 4.5 $0.00000 $0.00036

Measured yesterday against content hash c3ffad48e762, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

copy 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 yesterday.

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.

.cursor/rules/copy.mdc · 37 lines

What it actually says

Copy and prose (Caelus)

Before editing user-facing text, read docs/editorial-voice.md and docs/ai-slop-style-sheet.md.

Voice

  • Dry engineer, not pitch deck. Facts and measurements over adjectives.
  • Short sentences. Name sources and numbers.
  • No manifesto lines, mic-drops, or performed wit ("full stop", "mail to Zurich", "every layer needs its own referee").

Banned patterns

  • AI filler: delve, unpack, landscape, tapestry, testament, resonates, pivotal, holistic, "it's important to note"
  • Meta: "the lesson generalizes", "what this buys you", "cannot hide inside it", "the actual asset"
  • Em-dash chains — prefer comma, colon, or a new sentence

Workflow

  1. Edit copy in apps/web/ or docs/.
  2. Run npm run lint:prose and fix warnings.
  3. Do not rewrite package API docs or golden test commentary unless asked.

Terminology

  • Caelus (capitalized) for the project/engine in prose
  • caelus (lowercase) for the npm package name, imports (from "caelus"), and npm install caelus
  • Title case for page headings and nav labels
  • Emoji only in the home-page hero bullets and CTA labels; nowhere else
  • Swiss Ephemeris as oracle/referee, never as source code
  • clean-room sparingly; prefer "written from published sources"
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.

  1. yesterday First seen · 37 lines · 0 tokens per session scan A c3ffad48e762

Subscribe to this mod's changes

copy is a cursor rule published in the GitHub repository heavyblotto/caelus (0 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 365 tokens. 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.