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 OrcaQubits/agentic-commerce-skills-plugins --skill ap2-challenge-stepupgit clone --depth 1 https://github.com/OrcaQubits/agentic-commerce-skills-pluginsWrote 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/orcaqubits/agentic-commerce-skills-plugins/ap2-challenge-stepup)<a href="https://agentmods.dev/skills/orcaqubits/agentic-commerce-skills-plugins/ap2-challenge-stepup"><img src="https://agentmods.dev/badge/skills/orcaqubits/agentic-commerce-skills-plugins/ap2-challenge-stepup.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 | $0.00044 | $0.00962 |
| Opus 5 | $0.00022 | $0.00481 |
| Sonnet 5 | $0.00009 | $0.00192 |
| Haiku 4.5 | $0.00004 | $0.00096 |
Grade A, and why
ap2-challenge-stepup 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 8d 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 — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AP2 Challenge and Step-Up Flows
Before writing code
Fetch live docs:
- Fetch
https://ap2-protocol.org/specification/for challenge flow specification - Web-search
site:github.com google-agentic-commerce AP2 challenge OTP 3DS step-upfor implementation examples - Fetch
https://ap2-protocol.org/topics/privacy-and-security/for security context - Web-search
ap2 protocol 3DS2 OTP challenge redirectfor integration details
Conceptual Architecture
What Challenges Are
Challenges are additional authentication steps that any participant in the payment ecosystem can require during an AP2 transaction. They provide an extra layer of security beyond the mandate signatures.
When Challenges Occur
Any ecosystem participant may trigger a challenge:
- Payment Network — Requires 3DS2 for high-risk transactions
- Issuer/Bank — Requires OTP or biometric for verification
- Merchant — Requires confirmation for unusual orders
- Credentials Provider — Requires step-up for new payment methods
V0.1 Supported Challenge Types
AP2 V0.1 supports redirect challenges:
- 3DS2 (3D Secure 2.0) — Card network strong customer authentication
- OTP (One-Time Password) — SMS/email/app verification codes
- User is redirected to a trusted surface (not the agent) for resolution
Challenge Flow
1. Payment processing initiated
2. Network/Issuer determines challenge required
3. Challenge request returned to MPP
4. MPP sends challenge to Merchant Agent
5. Merchant Agent forwards to Shopping Agent (via A2A)
6. Shopping Agent redirects user to trusted surface
7. User completes challenge (enters OTP, completes 3DS)
8. Trusted surface confirms completion
9. Shopping Agent receives confirmation
10. Flow resumes from where the challenge was triggered
Redirect Pattern
The redirect challenge follows this pattern:
- Shopping Agent can't handle the challenge itself (security)
- User is redirected to the challenger's trusted surface
- This is a separate UI/page, not an agent conversation
- User interacts directly with the challenger's system
- Completion triggers a callback/redirect back to the flow
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.
- 8d ago First seen · 111 lines · 44 tokens per session scan A d7d1f947cb0e
ap2-challenge-stepup is a skill published in the GitHub repository OrcaQubits/agentic-commerce-skills-plugins (39 stars, last pushed 3mo ago), licensed MIT. It adds 44 tokens to every session and 962 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 2026-08-30.
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