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 rileyhilliard/agentrc --skill architecting-systemsgit clone --depth 1 https://github.com/rileyhilliard/agentrcWrote 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/rileyhilliard/agentrc/architecting-systems)<a href="https://agentmods.dev/skills/rileyhilliard/agentrc/architecting-systems"><img src="https://agentmods.dev/badge/skills/rileyhilliard/agentrc/architecting-systems.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 5.1 | $0.00043 | $0.01001 |
| Opus 5 | $0.00022 | $0.00500 |
| Sonnet 5 | $0.00009 | $0.00200 |
| Haiku 4.5 | $0.00004 | $0.00100 |
Grade A, and why
architecting-systems 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 7d 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 — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Architecting Systems
Core principle: Small decisions made early compound into either clean systems or massive technical debt. Get the structure right and the system stays maintainable as it grows. Get it wrong and every change gets harder.
Topic Selection
Load the relevant reference based on what you're working on:
| Working on... | Load | File |
|---|---|---|
| Layers, vertical slices, file organization | Structure | references/structure.md |
| Interfaces, dependency inversion, contracts | Coupling | references/coupling.md |
| Bounded contexts, API design, module boundaries | Boundaries | references/boundaries.md |
| Async patterns, race conditions, queues | Concurrency | references/concurrency.md |
| Logging, health checks, metrics, tracing | Observability | references/observability.md |
Load multiple references when the task spans topics. For most greenfield work, start with Structure and Coupling.
Core Principles (All Topics)
Convention over invention
Default to established patterns, standard libraries, and proven conventions. Novel solutions carry hidden costs: documentation burden, onboarding friction, and maintenance surprises.
| Prefer | Over |
|---|---|
| Framework conventions | Custom project structures |
| Standard library tools | Bespoke utilities for solved problems |
| Established patterns (MVC, repository, etc.) | Clever abstractions |
| Boring technology that works | Exciting technology that might |
The test: If someone new joins the team, how quickly can they find things and understand the structure? If the answer involves a tour guide, the conventions aren't strong enough.
State management
State is where complexity hides. The more places state lives and the more things can mutate it, the harder the system is to reason about.
- Minimize mutable shared state. If two modules need the same data, one should own it and the other should request it.
- Keep state close to where it's used. Global state is almost never the answer.
- Make state changes explicit. Whether that's through events, reducers, or explicit setter methods, the "what changed and why" should be traceable.
- Single source of truth. Every piece of data should have one authoritative home. Derived data should be computed, not independently stored, unless there's a measured performance reason to cache or denormalize.
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 7d ago First seen · 85 lines · 43 tokens per session scan A 4bd85d95a551
architecting-systems is a skill published in the GitHub repository rileyhilliard/agentrc (3 stars, last pushed 6mo ago), licensed MIT. It adds 43 tokens to every session and 1,001 once invoked, about $0.0002 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 2026-08-31.
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