wrdn-effect-schema-boundaries

A coding rule for checking untrusted or loosely typed data at the point where it enters a program, using Effect Schema, named checks, or typed adapters.

In plain words
What is it for?
Use it when handling JSON, API responses, configuration, or other unknown values in TypeScript code, especially when lint reports unsafe casts or property checks.
Why use it?
It removes repeated guesses and unsafe type casts by turning unknown input into a verified type once.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/usefulsoftwareco/executor/wrdn-effect-schema-boundaries
Any agent
npx skills add UsefulSoftwareCo/executor --skill wrdn-effect-schema-boundaries
Clone the repo
git clone --depth 1 https://github.com/UsefulSoftwareCo/executor

Made for: Claude Code, Codex.

Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 355 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00051 $0.00355
Opus 5 $0.00026 $0.00178
Sonnet 5 $0.00010 $0.00071
Haiku 4.5 $0.00005 $0.00036

Measured 2d ago against content hash aae568a8b337, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

wrdn-effect-schema-boundaries 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 2d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

.agents/skills/wrdn-effect-schema-boundaries/SKILL.md · 45 lines

What it actually says

You fix one pattern: domain code is asserting or probing an unknown shape instead of parsing it once at the boundary.

Fix Shape

  • Prefer Schema.decodeUnknownEffect(MySchema)(value) for untrusted input.
  • Prefer Schema.decodeUnknownEffect(Schema.fromJsonString(MySchema))(text) or Schema.decodeUnknownOption(Schema.parseJson())(text) for JSON strings.
  • Keep domain code typed after the decode; do not keep unknown and probe it repeatedly.
  • Replace JSON.parse, value as string, as unknown as X, as Record<string, unknown>, inline object assertions, "field" in value, and Reflect.get with a schema, typed adapter, or named guard.
  • A named guard is acceptable only when parsing is not the right abstraction and the guard has a precise return type.

Good

const ParsedConfig = Schema.Struct({
  endpoint: Schema.String,
});

const config = yield * Schema.decodeUnknownEffect(ParsedConfig)(raw);
const config = yield * Schema.decodeUnknownEffect(Schema.fromJsonString(ParsedConfig))(rawText);

Bad

const config = raw as unknown as { endpoint: string };
const config = JSON.parse(rawText) as { endpoint: string };
const pattern = updated.pattern as string;
Changes

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.

  1. 2d ago First seen · 45 lines · 51 tokens per session scan A aae568a8b337

Subscribe to this mod's changes

wrdn-effect-schema-boundaries is a skill published in the GitHub repository UsefulSoftwareCo/executor (3,494 stars, last pushed today), licensed MIT. It adds 51 tokens to every session and 355 once invoked, about $0.0003 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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