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.
npx skills add mendixlabs/mxcli --skill write-rulesgit clone --depth 1 https://github.com/mendixlabs/mxcliWrote 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.
[](https://agentmods.dev/skills/mendixlabs/mxcli/write-rules)<a href="https://agentmods.dev/skills/mendixlabs/mxcli/write-rules"><img src="https://agentmods.dev/badge/skills/mendixlabs/mxcli/write-rules/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.
<a href="https://agentmods.dev/skills/mendixlabs/mxcli/write-rules"><img src="https://agentmods.dev/badge/skills/mendixlabs/mxcli/write-rules.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high System Prompt Leakage · line 98 Skill contains instructions that could directly expose system prompts, internal rules, or hidden instructions to users or external parties.Fix: Remove any instructions that reveal, print, or output system prompts or internal rules. System instructions should never be exposed to end users.
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 | $0.00046 | $0.01699 |
| Opus 5.5 | $0.00018 | $0.00680 |
| Sonnet 5.5 | $0.00009 | $0.00340 |
| Haiku 4.5 | $0.00005 | $0.00170 |
Grade A, and why
write-rules 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 5d 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.
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.
How it starts
The opening of the file, as written. The whole thing — 159 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Find it fast
sed -n '<from>,<to>p' SKILL.md one section rather than reading the file;
./mxcli syntax <topic> answers how do I write this for a fraction of either.
| lines | section |
|---|---|
| 29-38 | When to Use This Skill |
| 39-52 | When to Use a Rule vs a Microflow |
| 53-67 | Key Differences from Microflows |
| 68-111 | Syntax |
| 112-129 | Reading and managing rules |
| 130-144 | What a rule may not contain |
| 145-155 | Validation checklist |
| 156-158 | Rules (LIST/DESCRIBE/CREATE [OR MODIFY]/DROP/MOVE RULE) |
Mendix Rule Skill
Guidance for writing Mendix rules in MDL. Mendix's own reference calls a rule "a special kind of microflow": it returns a Boolean or an enumeration, and it can only be used from a decision.
When to Use This Skill
- Writing
CREATE RULEstatements - Deciding whether logic belongs in a rule or a microflow
- Understanding what
mxcli checkrefuses in a rule body and why
The mirrors are write-microflows and write-nanoflows — a rule is the third flavour and shares their body syntax exactly.
When to Use a Rule vs a Microflow
| Scenario | Use |
|---|---|
| One condition, evaluated from several decisions | Rule |
| A named business condition the model should show by name | Rule |
| Choosing one of several enumerated outcomes from input | Rule |
| Anything that changes data | Microflow |
| Anything the user sees (page, message, download) | Microflow |
| Anything that talks to another system | Microflow |
Rule of thumb: a rule answers a question. The moment it needs to do something, it is a microflow.
Key Differences from Microflows
| Aspect | Microflow | Rule |
|---|---|---|
| Return type | Anything, including void | Boolean or enumeration — mandatory |
| Called from | Anywhere | A decision, and nowhere else |
| Changes data | Yes | No |
| Talks to the client | Yes | No |
| Integration | Yes | No |
| Module-role security | grant execute on microflow … |
None — a rule has no security to grant |
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.
- 5d ago Changed · +17 lines 65bf0a5a645c
- 15d ago Changed · +1 lines fb4ed00d1347
- 16d ago Changed cf09e64d8e6b
- 24d ago Changed · +4 lines 1cf707837e59
- 1mo ago First seen · 137 lines · 46 tokens per session scan A 624ef11fa44f
write-rules is a skill published in the GitHub repository mendixlabs/mxcli (131 stars, last pushed yesterday), licensed Apache-2.0. It adds 46 tokens to every session and 1,699 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-03.
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