A guided way to add a new behavior rule to a project's rule files. It reads the existing rules, chooses the right file when possible, and follows that file's writing conventions.

Use it to add a rule to a .claude/skills/*.rules.md file, including deciding when to ask which file should be changed.

It avoids putting rules in the wrong file or writing them in a format that conflicts with the project's existing instructions.

How causify-ai/helpers configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to causify-ai/helpers. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/causify-ai/helpers/master/.claude/skills/rules.add/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/causify-ai/helpers

Made for: Claude Code.

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/causify-ai/helpers/rules.add/github.svg)](https://agentmods.dev/skills/causify-ai/helpers/rules.add)

Your own site

<a href="https://agentmods.dev/skills/causify-ai/helpers/rules.add"><img src="https://agentmods.dev/badge/skills/causify-ai/helpers/rules.add/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/causify-ai/helpers/rules.add"><img src="https://agentmods.dev/badge/skills/causify-ai/helpers/rules.add.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 8 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 449 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe.

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	$0.00008	$0.00449
Opus 5.5	$0.00003	$0.00180
Sonnet 5.5	$0.00002	$0.00090
Haiku 4.5	$0.00001	$0.00045

Measured 1mo ago against content hash c77bb2891e58, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

rules.add scanned grade B with 1 finding 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 1mo 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.

Enumerates other installed skillsmediumAgent snooping

Other skills' SKILL.md files reveal prompts, capabilities and secrets that should be invisible to peers.

> ls -1 .claude/skills/*.rules.md

.claude/skills/rules.add/SKILL.md · 52 lines

What it actually says

Goal

The user passes:
- The description of a rule / behavior <CONTENT> to be added to a rule file
- (Optional) The target rule file to update <TARGET_RULE_FILE> in the format .claude/skills/*.rules.md

Workflow

Read Skill Rules

Read .claude/skills/skill.rules.md about conventions and rules to write skills

Determine Target Rule File

If the user didn't specify <TARGET_RULE_FILE>, decide which of the files <TARGET_RULE_FILE> the new rule needs to be added to, based on the content of <CONTENT>
The available rules are:
```
> ls -1 .claude/skills/*.rules.md
```
If <CONTENT> fits more than one rule file equally well, or fits none of them clearly, do not guess: ask the user which <TARGET_RULE_FILE> to use, listing the candidate files

Read Target Rule File

Read the target rules file <TARGET_RULE_FILE> to understand its structure and existing rules

Draft the New Rule

Draft the proposed rule <CONTENT> to be added, following the conventions in:
- .claude/skills/markdown.rules.md
- .claude/skills/text.rules.md

Add the New Rule

Find the proper H1 header that is related to <CONTENT>
- See .claude/skills/skill.rules.md ## Keep Rules Organized in the Rule File
Add the rule <CONTENT> to <TARGET_RULE_FILE>, following the conventions in .claude/skills/skill.rules.md
Make sure there is no overlap with other rules

Verification

<CONTENT> is added under the correct H1 header in <TARGET_RULE_FILE>
No existing rule in <TARGET_RULE_FILE> already covers <CONTENT>
<TARGET_RULE_FILE> was confirmed with the user instead of guessed, if it was ambiguous

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.

1mo ago First seen · 52 lines · 8 tokens per session scan B c77bb2891e58

Subscribe to this mod's changes

rules.add is a skill published in the GitHub repository causify-ai/helpers (150 stars, last pushed today), licensed Apache-2.0. It adds 8 tokens to every session and 449 once invoked, about $0.0000 per session on Opus 5.5. A static security scan graded it B with 1 finding (enumerates other installed skills). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-16.

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helpers: Skill for Claude Code