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 theam/facility --skill maintainable-softwaregit clone --depth 1 https://github.com/theam/facilityWrote 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/theam/facility/maintainable-software)<a href="https://agentmods.dev/skills/theam/facility/maintainable-software"><img src="https://agentmods.dev/badge/skills/theam/facility/maintainable-software/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/theam/facility/maintainable-software"><img src="https://agentmods.dev/badge/skills/theam/facility/maintainable-software.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00047 | $0.00608 |
| Opus 5.5 | $0.00019 | $0.00243 |
| Sonnet 5.5 | $0.00009 | $0.00122 |
| Haiku 4.5 | $0.00005 | $0.00061 |
Grade A, and why
maintainable-software 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 — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Maintainable software
The cost of software is the cost of changing it later. Every rule here optimizes for the next reader and the next change, not for the author.
Simplicity
- Solve the problem in front of you. Speculative generality — the parameter nobody passes, the interface with one implementation — is debt with no loan.
- Prefer boring constructs. Cleverness needs a comment; boring code doesn't.
- One concept per unit: a function that needs "and" in its description is two functions.
Naming
- Names come from the domain, not the implementation:
settleInvoice, notprocessData2. - A name that needs a comment to be understood is the wrong name. Rename first, comment only for what code cannot say (constraints, why-not-the- obvious-way).
- Inconsistent vocabulary is a bug factory: one concept, one word, repo-wide.
Boundaries and interfaces
- Narrow interfaces, deep modules: expose the smallest surface that serves the caller; keep the complexity behind it.
- Dependencies point one way. A module that reaches into its consumers — or into globals — can't be tested or replaced.
- Side effects live at the edges; the core is data in, data out. If a function both computes and writes, split it.
Duplication
- Duplicate shape is fine; duplicate concept is not. Two functions that look alike but change for different reasons should stay apart; one business rule written twice will diverge and one copy will be wrong.
- Extract on the second real occurrence of the same concept, with a domain name. Extracting on resemblance creates the worst abstraction: the shared helper full of flags.
Errors
- Make failure explicit at the boundary: validate input where it enters, fail with a message the caller can act on, never swallow.
- Impossible states should be unrepresentable (types, schemas, constraints) rather than checked everywhere.
Tests
- Tests protect behavior, not implementation. A test that breaks on a rename is friction; a behavior change that breaks no test is a hole.
- Test the boundary you'd be afraid to change. If a bug got through, the first fix is the test that would have caught it.
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 · 68 lines · 47 tokens per session scan A 9a591dde28df
maintainable-software is a skill published in the GitHub repository theam/facility (82 stars, last pushed yesterday), licensed Apache-2.0. It adds 47 tokens to every session and 608 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 2026-08-30.
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