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 agentmods add skills/amadeusitgroup/otter/otter-rules-enginenpx skills add AmadeusITGroup/otter --skill otter-rules-enginegit clone --depth 1 https://github.com/AmadeusITGroup/otterWrote 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/amadeusitgroup/otter/otter-rules-engine)<a href="https://agentmods.dev/skills/amadeusitgroup/otter/otter-rules-engine"><img src="https://agentmods.dev/badge/skills/amadeusitgroup/otter/otter-rules-engine.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00091 | $0.02767 |
| Opus 5 | $0.00046 | $0.01384 |
| Sonnet 5 | $0.00018 | $0.00553 |
| Haiku 4.5 | $0.00009 | $0.00277 |
Grade A, and why
otter-rules-engine 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 — 209 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Otter Rules Engine
The Otter rules engine (@o3r/rules-engine) is a client-side mechanism that evaluates a sorted list of Rulesets and applies actions based on the application's runtime context. When building or editing rules-engine artifacts, follow the workflow below so facts, operators, actions, and rulesets stay consistent and correctly registered.
When to Use
- Authoring or editing a Ruleset JSON file
- Adding a custom fact, operator, or action
- Making component behavior conditional at runtime (config, translation, asset, placeholder)
- Debugging why a rule does not trigger
Concept Map
| Concept | What it is | How to create |
|---|---|---|
| Ruleset | Sorted list of rules; may be gated by validityRange / linkedComponents |
Hand-authored/generated JSON validated by the ruleset schema |
| Rule | Tree of IF_ELSE blocks (branches) ending in ACTION blocks (leaves), identified by a unique id |
Inside the Ruleset JSON |
| Operator | Pure function evaluating a condition (up to two operands) | ng g @o3r/rules-engine:operator |
| Fact | A stream of business values (value$) that triggers re-evaluation |
ng g @o3r/rules-engine:facts-service |
| Action | Side effect applied at runtime, identified by a unique actionType |
Built-in, or a custom RulesEngineActionHandler |
Prerequisites
Requires an Otter-based app with @o3r/rules-engine installed (ng add @o3r/rules-engine) and the runner registered via provideRulesEngineRunner() (see below). To enable rules-engine on an existing Otter component, run the schematic rather than wiring it by hand:
ng g @o3r/rules-engine:rules-engine-to-component --path=<path-to-component-class.ts>
Decision: What Do You Need to Create?
What is missing to express the rule?
├── A business value the condition depends on → create a FACT
├── A comparison the built-in operators don't cover → create an OPERATOR
├── A runtime effect not covered by built-ins → create an ACTION handler
└── Only the logic itself → edit the RULESET JSON only
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 First seen · 209 lines · 91 tokens per session scan A 8de1e8b5dd04
otter-rules-engine is a skill published in the GitHub repository AmadeusITGroup/otter (57 stars, last pushed today), licensed BSD-3-Clause. It adds 91 tokens to every session and 2,767 once invoked, about $0.0005 per session on Opus 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 2026-08-30.
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