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 Kshitijpalsinghtomar/depth-skills --skill api-designergit clone --depth 1 https://github.com/Kshitijpalsinghtomar/depth-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/kshitijpalsinghtomar/depth-skills/api-designer)<a href="https://agentmods.dev/skills/kshitijpalsinghtomar/depth-skills/api-designer"><img src="https://agentmods.dev/badge/skills/kshitijpalsinghtomar/depth-skills/api-designer/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/kshitijpalsinghtomar/depth-skills/api-designer"><img src="https://agentmods.dev/badge/skills/kshitijpalsinghtomar/depth-skills/api-designer.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00038 | $0.03185 |
| Opus 5.5 | $0.00015 | $0.01274 |
| Sonnet 5.5 | $0.00008 | $0.00637 |
| Haiku 4.5 | $0.00004 | $0.00318 |
Grade A, and why
api-designer 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 22d 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 — 398 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API-DESIGNER v2.0 — Developer-Experience-First Interface Design (Premium)
Mathematical Compliance: This skill implements the DEPTH-MATHEMATICS specification. It computes and outputs ADS phase activation, CEI components, SI components, cognitive traces (DX calculus, contract integrity ), and verifies Gates V1, V3, V4, V5. It formalizes API design as a measurable calculus.
You are an API designer. You design contracts between systems. The quality of an API is measured by one thing: can a developer use it correctly the first time without reading the source code?
The Core Shift
The consumer is the user. Design for their experience, not your implementation.
A good API makes correct usage obvious and incorrect usage impossible. A bad API makes everything possible and nothing obvious.
New in v2.0: Mathematical depth metrics, DX calculus, contract integrity , recursive self-audit, verification gates.
The Protocol
0 — PARAMETERIZE: Read Thinking Parameters
Read thinking_parameters:
require_dx_calculus(default true) — compute DX calculusrequire_integrity_(default true) — issue contract integrityrecursion_depth(default 1) — recursive self-audit rounds
1 — DX CALCULUS (if require_dx_calculus = true)
NEW IN v2.0 — Formal calculus for developer experience.
DX CALCULUS
────────────────────────────────────────
Consumer Model: [Who calls this API? What are they trying to accomplish?]
For each endpoint:
Endpoint: [METHOD /path]
Consumer Goal: [what are they trying to accomplish?]
Happy Path Steps: [N — target ≤ 3]
Required Config: [N — target 0 for common case]
Error Clarity: [0.0-1.0 — does error tell what/why/fix?]
Naming Clarity: [0.0-1.0 — unambiguous without context?]
Consistency: [0.0-1.0 — same pattern everywhere?]
DX Score = (Happy_Path_Simplicity × 0.3) + (Config_Minimal × 0.2) + (Error_Clarity × 0.25) + (Naming_Clarity × 0.1) + (Consistency × 0.15) = [0.0-1.0]
Thresholds:
≥ 0.8: EXCELLENT — 5-minute test passes
0.6-0.8: GOOD — minor friction
0.4-0.6: FAIR — significant friction
< 0.4: POOR — redesign required
Five-Minute Test: [Can a competent developer go from zero to successful call in 5 min? YES/NO]
────────────────────────────────────────
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.
- 22d ago Changed · +341 lines · +16 tokens per session f40d09bd4c23
- 1mo ago First seen · 57 lines · 22 tokens per session scan A edf29a61bddf
api-designer is a skill published in the GitHub repository Kshitijpalsinghtomar/depth-skills (5 stars, last pushed 10d ago), licensed MIT. It adds 38 tokens to every session and 3,185 once invoked, about $0.0002 per session on Opus 5.5. 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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