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/abstractonion/cadence/explicit-undefinednpx skills add abstractonion/cadence --skill explicit-undefinedgit clone --depth 1 https://github.com/abstractonion/cadenceWrote 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/abstractonion/cadence/explicit-undefined)<a href="https://agentmods.dev/skills/abstractonion/cadence/explicit-undefined"><img src="https://agentmods.dev/badge/skills/abstractonion/cadence/explicit-undefined.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 | $0.00036 | $0.00224 |
| Opus 5 | $0.00018 | $0.00112 |
| Sonnet 5 | $0.00007 | $0.00045 |
| Haiku 4.5 | $0.00004 | $0.00022 |
Grade A, and why
explicit-undefined 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 4d 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.
What it actually says
TypeScript: prefer explicit | undefined over optional ?:
For data-shaped fields and props that callers must reason about, type them as T | undefined rather than field?: T.
Prefer
type Props = {
projectId: string | undefined;
user: User | undefined;
};
Avoid
type Props = {
projectId?: string;
user?: User;
};
Why
Explicit | undefined forces every caller to make a deliberate decision about the missing case. Optional ?: lets callers silently forget the field exists, which masks bugs.
When ?: is fine
Pure UI affordance flags where "omitted" obviously means "off": showHeader?, disabled?, hideFooter?. These don't carry data and have a sensible default-false interpretation.
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.
- 4d ago First seen · 35 lines · 36 tokens per session scan A e1c25bebc2ac
explicit-undefined is a skill published in the GitHub repository abstractonion/cadence (4 stars, last pushed 2mo ago), licensed MIT. It adds 36 tokens to every session and 224 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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