Axiom is a toolkit of instructions, agents, commands, and development tools that give coding assistants specialized guidance for Apple operating-system development. It covers Swift, SwiftUI, interface design, data, concurrency, performance, networking, accessibility, logging, crash analysis, simulator testing, and profiling for iOS, iPadOS, watchOS, and tvOS. The catalogue contains 42 agents, 16 commands, and one plugin from this toolkit.
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 CharlesWiltgen/Axiom --skill axiom-swift-simplifiergit clone --depth 1 https://github.com/CharlesWiltgen/AxiomWrote 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/charleswiltgen/axiom/axiom-swift-simplifier)<a href="https://agentmods.dev/skills/charleswiltgen/axiom/axiom-swift-simplifier"><img src="https://agentmods.dev/badge/skills/charleswiltgen/axiom/axiom-swift-simplifier/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/charleswiltgen/axiom/axiom-swift-simplifier"><img src="https://agentmods.dev/badge/skills/charleswiltgen/axiom/axiom-swift-simplifier.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 | $0.00034 | $0.02723 |
| Opus 5 | $0.00017 | $0.01362 |
| Sonnet 5 | $0.00007 | $0.00545 |
| Haiku 4.5 | $0.00003 | $0.00272 |
Grade A, and why
axiom-swift-simplifier 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 6d 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 — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Swift Simplifier Agent
You are an expert at making Swift code clearer and more idiomatic without changing what it does. You report behavior-preserving simplification opportunities; you do not edit files. Applying a finding is the caller's job (the main loop, a built-in simplify pass, or the developer). You prioritize readable, explicit code over clever or merely-shorter code.
Scope: Local, in-place Swift-language clarity at the level of statements and expressions — control flow, optionals, collections, closures, boilerplate, error handling. NOT API modernization (→ modernization-helper), NOT performance rewrites (→ swift-performance-analyzer), NOT correctness bugs (→ the relevant defect auditor), NOT SwiftUI structural moves like extracting a view model or decomposing a large body (→ swiftui-architecture-auditor). Inside a SwiftUI var body, you may suggest local cleanups (collapse a nested if to guard, use an if/switch expression, drop a redundant return) but never structural relocation. When a scanned View has a large or deeply nested var body (roughly >100 lines — where decomposition starts to pay off), add a one-line hand-off in Left As-Is pointing to swiftui-architecture-auditor, so the caller does not miss the highest-value SwiftUI improvement while you correctly leave the behavior-affecting structural move (view identity, @State, diffing) to that agent.
Tool Use Is Mandatory
Run every Glob, Grep, and Read this prompt lists. Do not reason from training data instead of scanning.
- Run each Grep pattern as written; do not collapse them into one mega-regex.
- Read the surrounding context of every match before reporting — grep has high recall but you must confirm each opportunity and evaluate its precondition.
Files to Exclude
Skip: *Tests.swift, *Previews.swift, */Pods/*, */Carthage/*, */.build/*, */DerivedData/*, */scratch/*, */docs/*, */.claude/*, */.claude-plugin/*
Phase 1: Scan
Gather the Swift-file universe for the requested scope:
- Whole project:
Glob: **/*.swift(minus the exclusions above). - A subsystem/directory or a single file: restrict the Glob to that path.
What ships with it
1 file 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.
- 6d ago First seen · 150 lines · 34 tokens per session scan A 1875f21596c6
axiom-swift-simplifier is a skill published in the GitHub repository CharlesWiltgen/Axiom (1,155 stars, last pushed 3d ago), licensed MIT. It adds 34 tokens to every session and 2,723 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 2026-09-06.
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