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 TalissonVitorino/kmp-ios-skills --skill core-nfcgit clone --depth 1 https://github.com/TalissonVitorino/kmp-ios-skillsWrote 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/talissonvitorino/kmp-ios-skills/core-nfc)<a href="https://agentmods.dev/skills/talissonvitorino/kmp-ios-skills/core-nfc"><img src="https://agentmods.dev/badge/skills/talissonvitorino/kmp-ios-skills/core-nfc/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/talissonvitorino/kmp-ios-skills/core-nfc"><img src="https://agentmods.dev/badge/skills/talissonvitorino/kmp-ios-skills/core-nfc.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 7 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Rogue Agent · line 19 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 30 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 37 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 38 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 286 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 292 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium Rogue Agent · line 293 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
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 | $0.00247 | $0.04101 |
| Opus 5 | $0.00123 | $0.02050 |
| Sonnet 5 | $0.00049 | $0.00820 |
| Haiku 4.5 | $0.00025 | $0.00410 |
Grade A, and why
core-nfc 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 11d 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 — 303 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CoreNFC (iOS / iPadOS)
Detect, read, and write NFC tags on iPhone (7 and later; background reading iPhone XS
and later). Two session types, both built on NFCReaderSession:
-
NFCNDEFReaderSession— high-level NDEF read/write. Use for NFC Forum Type 1–5 tags carrying URLs, text, vCards. Simplest path. -
NFCTagReaderSession— low-level access to.iso7816,.iso15693,.feliCa,.miFaretags for raw commands/APDUs (transit, access cards, custom protocols). -
Not CoreNFC: Apple Pay / Wallet passes are on the Secure Element and unreadable by third-party apps — see
passkit. Host Card Emulation is a separate entitlement +CardSessionAPI, out of scope here. -
KMP: CoreNFC is iOS-only; expose a
commonMaininterface and bind a Swiftactual(seeexpect-actual,kmp-ios-integration). Keep tag payloads/secrets off shared plaintext — route sensitive material throughswift-security.
Contents
- Setup: entitlement + Info.plist
- NDEF reading
- NDEF writing
- Building NDEF payloads
- Tag reader session (raw tags)
- Session lifecycle & errors
- Background tag reading
- Correctness checklist
- References:
references/tag-types.md,references/background-and-entitlements.md
Setup: entitlement + Info.plist
Both are mandatory — a missing usage string crashes on begin(); a missing entitlement fails session creation.
- Entitlement
com.apple.developer.nfc.readersession.formats(add the Near Field Communication Tag Reading capability in Xcode). Array of strings:"NDEF"— enablesNFCNDEFReaderSession."TAG"— enablesNFCTagReaderSession(raw ISO7816/ISO15693/FeliCa/MIFARE). Include both if you use both session types.
- Info.plist
NFCReaderUsageDescription(String) — required, shown in the scan sheet. Explain why you scan. - Info.plist application-identifier lists (needed to detect certain tags):
com.apple.developer.nfc.readersession.iso7816.select-identifiers— array of AIDs (hex strings) for ISO7816 tags.com.apple.developer.nfc.readersession.felica.systemcodes— array of FeliCa system codes.
- Availability gate — check before offering NFC UI:
What ships with it
2 files 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.
- 11d ago First seen · 303 lines · 247 tokens per session scan A 033b15fb4619
core-nfc is a skill published in the GitHub repository TalissonVitorino/kmp-ios-skills (12 stars, last pushed 16d ago), licensed MIT. It adds 247 tokens to every session and 4,101 once invoked, about $0.0012 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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