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.
git clone --depth 1 https://github.com/lucamezzalira/mfe-skillsWrote 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/rules/lucamezzalira/mfe-skills/mfe-boundary-rules-core-critical)<a href="https://agentmods.dev/rules/lucamezzalira/mfe-skills/mfe-boundary-rules-core-critical"><img src="https://agentmods.dev/badge/rules/lucamezzalira/mfe-skills/mfe-boundary-rules-core-critical/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/rules/lucamezzalira/mfe-skills/mfe-boundary-rules-core-critical"><img src="https://agentmods.dev/badge/rules/lucamezzalira/mfe-skills/mfe-boundary-rules-core-critical.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00033 | $0.01099 |
| Opus 5.5 | $0.00013 | $0.00440 |
| Sonnet 5.5 | $0.00007 | $0.00220 |
| Haiku 4.5 | $0.00003 | $0.00110 |
Grade A, and why
mfe-boundary-rules-core-critical 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 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.
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 — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MFE boundary rules — critical (rules 3 and 4)
Contents
- Rule 3 — Hides implementation details behind an API contract
- Rule 4 — Communicates via events, not shared state
Version: 1.3 | Skill: reviewing-mfe-boundaries | Source: Building Micro-Frontends (O'Reilly).
Critical rules: hide implementation details; communicate via events not shared state.
For rules 1, 2, 5–8 and governance extensions: load references/rules-core-standard.md.
For framework-specific patterns: load references/rules-toolchain.md.
Rule 3 — Hides implementation details behind an API contract
Define the API contract upfront between producer and consumer teams. Internal implementation details — frameworks, data fetching strategies, database schemas, code structure — stay hidden behind it.
The API-first principle: the contract is the binding agreement. Both teams can work in parallel, focused on their side of the contract. Either team can change their internals freely without affecting the other, as long as the contract is respected.
Strong encapsulation is required to avoid domain leaks into other parts of the application. When a micro-frontend exposes its internals — through direct imports, shared modules, or coupled data structures — changes inside cascade outside and independent deployment breaks down.
Violation signals:
- Direct imports from one micro-frontend's source into another
- Shared internal modules or utilities across micro-frontend boundaries
- Contract changes that require simultaneous updates across multiple teams
- A micro-frontend exposing more than what consumers strictly need
Code-checkable patterns:
// ✗ CRITICAL — cross-boundary import, bypasses the API contract
import { UserStore } from '@org/auth-mfe/store'
import { useCart } from '@org/cart-mfe/hooks'
import { formatCurrency } from '@org/checkout-mfe/utils'
// ✓ Each micro-frontend accesses only its own internals
import { formatCurrency } from './utils/currency'
// ✓ Shared utilities belong in an npm package, not a micro-frontend
import { formatCurrency } from '@org/shared-utils'
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 · 109 lines · 1,099 tokens per session scan A e29913c06cce
mfe-boundary-rules-core-critical is a cursor rule published in the GitHub repository lucamezzalira/mfe-skills (53 stars, last pushed 1mo ago), licensed MIT. It adds 33 tokens to every session and 1,099 once invoked, about $0.0001 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 2026-09-23.
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