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 pproenca/dot-skills --skill stripe-inspired-api-design-rulesgit clone --depth 1 https://github.com/pproenca/dot-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/pproenca/dot-skills/stripe-inspired-api-design-rules)<a href="https://agentmods.dev/skills/pproenca/dot-skills/stripe-inspired-api-design-rules"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/stripe-inspired-api-design-rules/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/pproenca/dot-skills/stripe-inspired-api-design-rules"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/stripe-inspired-api-design-rules.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 | $0.00129 | $0.02783 |
| Opus 5 | $0.00064 | $0.01392 |
| Sonnet 5 | $0.00026 | $0.00557 |
| Haiku 4.5 | $0.00013 | $0.00278 |
Grade A, and why
stripe-inspired-api-design-rules 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 5d 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 — 134 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Stripe-Inspired API Design Best Practices
A reference distillation of the design conventions behind Stripe's API — the most widely admired and copied JSON HTTP API in the industry. Contains 52 actionable rules across 8 categories, prioritised by how irreversibly a wrong decision cascades through every endpoint, every SDK, and every client integration. Each rule explains the WHY, shows incorrect-vs-correct code, and links to the canonical source.
When to Apply
Reach for this skill when:
- Designing a new JSON HTTP API or a new endpoint on an existing one
- Reviewing an API design proposal, OpenAPI spec, or PR that adds/changes endpoints
- Debugging an integration where the "wrong" shape of the API is causing client bugs
- Auditing an API for naming consistency, error shape uniformity, or compatibility risks
- Producing an API design report (the kind your inspector tool emits —
Critical / Warning / Suggestion / Positive) - Picking between two designs and looking for an authoritative source to back the choice
- Onboarding to API design — these are the canonical patterns to internalise first
The rules are general — they apply to any JSON HTTP API, not just APIs imitating Stripe. Triggers include "API design", "OpenAPI", "endpoint", "schema", "webhook", "idempotency", "pagination", "API versioning", and reviews of YAML/JSON spec files.
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Resource Modeling & Identifiers | CRITICAL | resource- |
| 2 | URL Structure & HTTP Semantics | CRITICAL | url- |
| 3 | Request & Response Format | HIGH | format- |
| 4 | Errors & Status Codes | HIGH | error- |
| 5 | Idempotency & Safe Retries | HIGH | idem- |
| 6 | Versioning & Backwards Compatibility | HIGH | ver- |
| 7 | Naming, Polymorphism & Metadata | MEDIUM-HIGH | naming- |
| 8 | Authentication, Webhooks & Search | MEDIUM-HIGH | ops- |
Earlier categories cascade harder: a wrong choice in resource modeling (numeric IDs, no object discriminator) propagates to every endpoint forever; a wrong choice in webhook event naming is a single category to fix.
What ships with it
57 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.
- AGENTS.md 13 KB
- assets/templates/_template.md 3.7 KB
- gotchas.md 550 B
- metadata.json 1.4 KB
- references/_sections.md 3.2 KB
- references/error-doc-url-on-every-error.md 3.7 KB
- references/error-four-type-enum.md 4.1 KB
- references/error-http-status-mapping.md 4.0 KB
- references/error-lowercase-snake-case-codes.md 2.8 KB
- references/error-message-mandatory-code-optional.md 3.7 KB
- references/error-top-level-object.md 3.5 KB
- references/format-bracket-notation-nesting.md 2.9 KB
- references/format-cursor-pagination.md 3.0 KB
- references/format-dot-notation-expansion.md 3.1 KB
- references/format-expand-parameter.md 3.6 KB
- references/format-form-encoded-requests.md 3.1 KB
- references/format-list-envelope.md 3.0 KB
- references/format-no-total-counts.md 2.6 KB
- references/idem-24h-ttl.md 3.5 KB
- references/idem-fail-on-key-reuse.md 4.6 KB
- references/idem-key-header.md 3.8 KB
- references/idem-recovery-points.md 4.9 KB
- references/idem-scoped-per-account.md 3.3 KB
- references/naming-american-english.md 3.9 KB
- references/naming-boolean-past-tense.md 3.4 KB
- references/naming-enums-over-booleans.md 4.3 KB
- references/naming-metadata-pattern.md 4.5 KB
- references/naming-simple-unambiguous.md 4.1 KB
- references/naming-snake-case-wire-format.md 3.4 KB
- references/naming-type-discriminator-polymorphism.md 4.6 KB
- references/ops-https-only-basic-auth.md 3.9 KB
- references/ops-on-behalf-of-header.md 4.6 KB
- references/ops-prefixed-api-keys.md 4.7 KB
- references/ops-webhook-at-least-once-handlers-idempotent.md 6.3 KB
- references/ops-webhook-event-envelope.md 4.9 KB
- references/ops-webhook-event-naming.md 5.0 KB
- references/ops-webhook-signature.md 5.5 KB
- references/resource-birthdate-hash.md 2.5 KB
- references/resource-currency-field-not-name.md 2.5 KB
- references/resource-decimal-suffix-strings.md 2.6 KB
- references/resource-integer-minor-units.md 2.6 KB
- references/resource-iso-date-only.md 2.3 KB
- references/resource-object-discriminator.md 2.1 KB
- references/resource-opaque-ids.md 2.3 KB
- references/resource-prefixed-string-ids.md 2.3 KB
- references/resource-unix-seconds-timestamps.md 2.2 KB
- references/url-action-verbs-as-subpaths.md 2.8 KB
- references/url-dedicated-search-endpoint.md 2.9 KB
- references/url-no-bulk-endpoints.md 2.9 KB
- references/url-plural-collections.md 2.2 KB
- references/url-post-for-updates.md 2.6 KB
- references/url-version-in-path-and-header.md 2.7 KB
- references/ver-account-pinning.md 3.7 KB
- references/ver-additive-changes.md 4.9 KB
- references/ver-dated-versions.md 3.4 KB
- references/ver-tolerate-unknown.md 5.3 KB
- references/ver-version-change-modules.md 5.0 KB
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.
- 5d ago First seen · 134 lines · 129 tokens per session scan A ed9bb6363cf6
stripe-inspired-api-design-rules is a skill published in the GitHub repository pproenca/dot-skills (205 stars, last pushed 24d ago), licensed MIT. It adds 129 tokens to every session and 2,783 once invoked, about $0.0006 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 2026-09-03.
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