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 SwiftfulThinking/SwiftfulStarterProject --skill creating-ab-testgit clone --depth 1 https://github.com/SwiftfulThinking/SwiftfulStarterProjectWrote 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/swiftfulthinking/swiftfulstarterproject/creating-ab-test)<a href="https://agentmods.dev/skills/swiftfulthinking/swiftfulstarterproject/creating-ab-test"><img src="https://agentmods.dev/badge/skills/swiftfulthinking/swiftfulstarterproject/creating-ab-test.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 5.1 | $0.00064 | $0.00859 |
| Opus 5 | $0.00032 | $0.00430 |
| Sonnet 5 | $0.00013 | $0.00172 |
| Haiku 4.5 | $0.00006 | $0.00086 |
Grade A, and why
creating-ab-test 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.
How it starts
The opening of the file, as written. The whole thing — 59 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Creating AB Test
Wire a new AB test through all required files. This is a multi-file mechanical change — every test follows the same pattern across 5+ files.
Steps
- Get the test name from the user (camelCase, e.g.,
showBanner,paywallVariant) - Determine the test type — Bool (on/off) or enum (multiple variants)
- If enum, create the option enum file first
- Read references/checklist.md for the exact code to add in each file
- Update all files in order
Test Type
| Type | When | Example |
|---|---|---|
| Bool | Simple on/off flag | showBanner: Bool |
| Enum | Multiple variants | paywallVariant: PaywallTestOption |
For enum tests, create a {TestName}Option.swift file in Managers/ABTests/Models/ with String, Codable, CaseIterable conformance and a static var default.
Files to Update (in order)
| # | File | What to Add |
|---|---|---|
| 1 | Managers/ABTests/Models/ActiveABTests.swift |
Property, init param, CodingKey, eventParameters, update method, RemoteConfig init, asNSObjectDictionary |
| 2 | All files in Managers/ABTests/Services/ |
Each service conforming to ABTestService must be updated to handle the new test property (see below) |
| 3 | Core/DevSettings/DevSettingsPresenter.swift |
State property, loadABTests line, change handler |
| 4 | Core/DevSettings/DevSettingsView.swift |
Toggle (Bool) or Picker (enum) in abTestSection |
| 5 | Root/RIBs/Core/CoreInteractor.swift |
Computed property exposing the test value |
Updating Service Files
List all files in Managers/ABTests/Services/ and update every one. The specific services may vary by project (e.g., MockABTestService, LocalABTestService, FirebaseABTestService, MixpanelABTestService, etc.). For each service, read the file and add the new test property following its existing pattern — mock services get an optional init param, local services get a @UserDefault, prod services get a default value.
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.
- yesterday First seen · 59 lines · 64 tokens per session scan A 40d6306ba44a
creating-ab-test is a skill published in the GitHub repository SwiftfulThinking/SwiftfulStarterProject (74 stars, last pushed 5mo ago), licensed MIT. It adds 64 tokens to every session and 859 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 2026-09-04.
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