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 sd0xdev/sd0x-harness --skill fp-briefgit clone --depth 1 https://github.com/sd0xdev/sd0x-harnessWrote 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/sd0xdev/sd0x-harness/fp-brief)<a href="https://agentmods.dev/skills/sd0xdev/sd0x-harness/fp-brief"><img src="https://agentmods.dev/badge/skills/sd0xdev/sd0x-harness/fp-brief/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/sd0xdev/sd0x-harness/fp-brief"><img src="https://agentmods.dev/badge/skills/sd0xdev/sd0x-harness/fp-brief.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 | $0.00077 | $0.01791 |
| Opus 5.5 | $0.00031 | $0.00716 |
| Sonnet 5.5 | $0.00015 | $0.00358 |
| Haiku 4.5 | $0.00008 | $0.00179 |
Grade A, and why
fp-brief 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 — 175 lines — stays where its author put it; the contents beside it link to each section on GitHub.
First-Principles Briefing Skill
Trigger
- Keywords: first principles, fp brief, why was this decided, reasoning chain, decision sensitivity, explain decisions, assumption analysis, onboarding brief
When NOT to Use
| Scenario | Alternative |
|---|---|
| PM/CTO executive summary (strip technical details) | /project-brief |
| Pre-doc feasibility analysis (before writing spec) | /feasibility-study |
| Code explanation at function/file level | /codex-explain |
| Code architecture overview | /code-explore |
| Simple document summary | Ask Claude directly |
Command Signature
/fp-brief <doc-path> [--depth brief|normal|deep] [--verify off|codex] [--output <path>] [--no-save]
| Flag | Default | Description |
|---|---|---|
<doc-path> |
Required | Source markdown document path |
--depth |
normal |
Output detail level |
--verify |
off |
Independent Codex reasoning verification |
--output |
Same dir, -fp-brief.md suffix |
Custom output path |
--no-save |
false | Print to stdout instead of file |
Workflow
sequenceDiagram
participant U as User
participant S as /fp-brief
participant D as Source Doc
participant O as Output File
participant X as Codex (optional)
U->>S: /fp-brief <doc-path> [--depth] [--verify]
Note over S: Phase 1: Input Resolution
S->>S: Validate path (repo boundary)
S->>D: Read source document
S->>S: Redaction scan (fail-safe)
S->>S: Auto-detect format (hybrid)
Note over S: Phase 2: First-Principles Extraction
S->>S: Extract Root Problem (5-Why)
S->>S: Build Assumptions Register
S->>S: Build Reasoning Chain
S->>S: Build Alternative Rejection Log
S->>S: Build Decision Sensitivity
S->>S: Identify Open Unknowns
Note over S: Phase 3: Output Assembly
S->>O: Write *-fp-brief.md
alt --verify codex
S->>X: Independent reasoning verification
X-->>S: Verification Delta
S->>O: Append Verification Delta
end
S-->>U: Report complete
What ships with it
4 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.
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 Changed c94ccc580fb9
- 1mo ago First seen · 175 lines · 77 tokens per session scan A e6934faa55c2
fp-brief is a skill published in the GitHub repository sd0xdev/sd0x-harness (194 stars, last pushed 13d ago), licensed MIT. It adds 77 tokens to every session and 1,791 once invoked, about $0.0003 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.
Other skills, from other repositories
guidance
A guide for answering questions about installing and configuring QwenPaw, a software tool with local documentation. It says to check those documents first and use official website information only when needed.
edu-math-tutorial
A Chinese-language guide for turning a maths problem into a step-by-step teaching video. It explains how to break down the solution, write narration, format equations, and structure scenes.
exploration
Two-mode exploration skill: (1) design dialogue — turn rough ideas into validated designs through collaborative interview before planning; (2) spike — throwaway code answering ONE design question, deleted or absorbed, never shipped. Router invokes mode via dispatch context.
building
Use when writing production code test-first: the RED-GREEN-REFACTOR cycle, false-RED detection, vertical slicing, scope escalation, test process discipline, and code generation patterns.
cc10x-guide
Answers questions about cc10x itself — what it is, how to install and configure it, how the router, workflows, memory, and hooks operate, and how to troubleshoot. Use this skill when: the user asks ABOUT cc10x — "what is cc10x", "how do I configure cc10x", "why isn't cc10x activating", "how do cc10x workflows work"…
diff-driven-docs
Use when a BUILD phase completes, a commit is staged, or a PR is about to be created, and the diff has not yet been reflected in documentation. Also use when the user says "update docs", "sync docs", "document this", or asks whether documentation is up to date.