types

A set of coding rules for keeping type information accurate and explicit. It treats compiler-silencing shortcuts, such as ignoring errors or using unsafe casts, as signs that the design needs fixing.

In plain words
What is it for?
It guides choices such as using grouped result types instead of multiple flags, matching the repository’s error-handling style, writing clear public function signatures, and deriving types from existing schemas.
Why use it?
It prevents hidden errors and unclear interfaces from being accepted just to make a build pass. It also keeps error handling and missing-value conventions consistent across a codebase.

Cursor rule

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 rules/kleosr/kleosrules/types
Clone the repo
git clone --depth 1 https://github.com/kleosr/kleosrules
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 163 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 $0.00000 $0.00163
Opus 5 $0.00000 $0.00081
Sonnet 5 $0.00000 $0.00033
Haiku 4.5 $0.00000 $0.00016

Measured yesterday against content hash 1bcffeaba3d3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

types 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 yesterday.

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.

shared/rules/types.mdc · 19 lines

What it actually says

Types

Fix the design; don't silence the compiler. Escape hatch = design bug. Do not add suppressions just to pass CI.

Prefer: sum types over parallel booleans; the repo's fallible-op idiom (Result, error returns, checked exceptions — match neighbors); explicit public signatures; schema-inferred types when schemas exist; one nullish convention per repo.

Language bans (any, blind casts, unwrap, ignored errors) live in TOOLCHAIN.md / Semgrep / Clippy when present — not re-stated here.

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. yesterday First seen · 19 lines · 0 tokens per session scan A 1bcffeaba3d3

Subscribe to this mod's changes

types is a cursor rule published in the GitHub repository kleosr/kleosrules (2 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 163 tokens. 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.