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 agentmods add skills/fullstack-phoenix/saas_kit/paymentsnpx skills add fullstack-phoenix/saas_kit --skill paymentsgit clone --depth 1 https://github.com/fullstack-phoenix/saas_kitWhat 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 | $0.00041 | $0.00912 |
| Opus 5 | $0.00020 | $0.00456 |
| Sonnet 5 | $0.00008 | $0.00182 |
| Haiku 4.5 | $0.00004 | $0.00091 |
Grade A, and why
payments 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 2d 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 — 126 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Payments
Installs a small billing facade behind a @callback so the app charges users
through one swappable provider implementation. The first available provider is
Stripe Subscription checkout: it creates hosted Stripe Checkout sessions over
Req, with no extra HTTP client dependency. You call
MyApp.Billing.checkout_url/2 from your own checkout route.
When to use
- The app needs paid plans — subscriptions or one-time purchases — and you want a provider-agnostic seam rather than Stripe calls scattered through controllers.
- You want hosted Checkout (Stripe redirects, collects card details) instead of building a payment form yourself.
- Don't reach for this if billing is free, or if you only need a static "contact sales" page with no charge flow.
Dependencies
- Requires:
authentication— billing is keyed to auser. - Recommended: None.
Install
mix saaskit.feature.install payments
The installer asks one decision:
- Which payment provider? (
provider) — required. The only current option isstripe_subscription, which installs the Stripe hosted-Checkout subscription implementation behind the facade.
mix saaskit.feature.install payments --decision provider=stripe_subscription
What it generates
lib/my_app/billing.ex— the billing facade. Defines thecreate_checkout_session/2@callback, the publiccheckout_url/2entry point, and a privateprovider/0that resolves the configured implementation.
Configuration
The facade resolves its provider from application config:
# config/config.exs
config :my_app, :billing,
provider: MyApp.Billing.StripeSubscription
Secrets come from the environment, not config files:
STRIPE_SECRET_KEY— your Stripe API secret.STRIPE_SUBSCRIPTION_PRICE_ID— the price the subscription Checkout charges.
For production, set both in the deployed environment and switch to your live Stripe keys.
Tweaking for your app
Call the facade from an authenticated checkout action and redirect to the hosted session:
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.
- 2d ago First seen · 126 lines · 41 tokens per session scan A aa75e61eeaa2
payments is a skill published in the GitHub repository fullstack-phoenix/saas_kit (2 stars, last pushed 2mo ago), licensed MIT. It adds 41 tokens to every session and 912 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 2026-08-31.
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