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 deepklarity/harness-kit --skill hk-mock-firstgit clone --depth 1 https://github.com/deepklarity/harness-kitWrote 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/deepklarity/harness-kit/hk-mock-first)<a href="https://agentmods.dev/skills/deepklarity/harness-kit/hk-mock-first"><img src="https://agentmods.dev/badge/skills/deepklarity/harness-kit/hk-mock-first/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/deepklarity/harness-kit/hk-mock-first"><img src="https://agentmods.dev/badge/skills/deepklarity/harness-kit/hk-mock-first.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 | $0.00126 | $0.03495 |
| Opus 5.5 | $0.00050 | $0.01398 |
| Sonnet 5.5 | $0.00025 | $0.00699 |
| Haiku 4.5 | $0.00013 | $0.00349 |
Grade A, and why
hk-mock-first 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 1mo 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 — 342 lines — stays where its author put it; the contents beside it link to each section on GitHub.
/hk-mock-first — Mock-First, Layer-by-Layer Feature Development
The traditional approach — build the plumbing, wire the API, then hope the UI works — inverts the feedback loop. You discover experience problems after committing to implementation choices. This skill inverts the flow: validate the experience first with realistic mocks, then progressively replace mocks with real code, one complexity layer at a time.
Why this matters: A feature that "works" but feels wrong is more expensive to fix than one that was never built. Mock-first means the human curates the experience before any plumbing exists. This directly serves the philosophy tenet of Taste as a Filter — the system produces options, the human filters. And Good Enough — you don't over-engineer layers that haven't been validated yet.
Context
<feature_context> $ARGUMENTS </feature_context>
If the context above is empty or unclear, ask the user:
- What feature or change are you building?
- Which user-facing interfaces does it touch? (UI pages, CLI output, API responses that drive UI)
- Where should the workspace live? (suggest
docs/mock-first/<feature-slug>/)
The Workspace
Everything lives on disk. The workspace is the product, not temp files — it's the organized record of what was mocked, what was accepted, and what's been deepened. It also serves as the resumption anchor: if the conversation compacts or a new session starts, the workspace contains everything needed to continue.
docs/mock-first/<feature-slug>/
├── tracker.md # Live state (the resumption anchor)
├── surface/
│ ├── interface-map.md # All user-facing interfaces this feature touches
│ ├── mock-data/ # Actual mock data files (JSON, fixtures, factories)
│ ├── mock-components/ # Mock UI components, stubs, or test pages (if applicable)
│ ├── states.md # All UI/interface states catalogued
│ └── acceptance.md # User's acceptance notes + screenshots
├── layer-1/
│ ├── boundary.md # What this layer is, where the complexity boundary sits
│ ├── test-plan.md # TDD: tests to write before implementation
│ ├── changes.md # What changed (files, diffs)
│ └── verification.md # Tests pass + interface still works
├── layer-2/
│ └── ...
└── summary.md # Written when feature ships (or when pausing long-term)
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.
- 1mo ago First seen · 342 lines · 126 tokens per session scan A 8da73f500881
hk-mock-first is a skill published in the GitHub repository deepklarity/harness-kit (102 stars, last pushed 3mo ago), licensed MIT. It adds 126 tokens to every session and 3,495 once invoked, about $0.0005 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 2026-08-30.
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