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 xcrft/mastermind --skill mastermind-investigation-ledgergit clone --depth 1 https://github.com/xcrft/mastermindWrote 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/xcrft/mastermind/mastermind-investigation-ledger)<a href="https://agentmods.dev/skills/xcrft/mastermind/mastermind-investigation-ledger"><img src="https://agentmods.dev/badge/skills/xcrft/mastermind/mastermind-investigation-ledger/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/xcrft/mastermind/mastermind-investigation-ledger"><img src="https://agentmods.dev/badge/skills/xcrft/mastermind/mastermind-investigation-ledger.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 | $0.00049 | $0.00804 |
| Opus 5 | $0.00024 | $0.00402 |
| Sonnet 5 | $0.00010 | $0.00161 |
| Haiku 4.5 | $0.00005 | $0.00080 |
Grade A, and why
mastermind-investigation-ledger 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 9d 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 — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Investigation ledger — confirm root cause before specifying
When a bug, test failure, or regression has no known cause, diagnose before specifying the fix. The ledger prevents premature closure while allowing independent evidence gathering when it is safe and useful.
When to use
Use when:
- "X is broken" with no stated why.
- A stack trace points to ≥ 2 plausible causes.
- Behavior changed and no obvious commit explains it.
- You catch yourself guessing ("probably the cache", "likely a race") without evidence.
Do NOT use when:
- The cause is already known (a typo, a wrong constant, a confirmed missing import) → go straight to a spec.
- It's a feature request, not a failure.
- The fix is a self-evident one-liner.
The ledger
Track every hypothesis explicitly:
| # | hypothesis | status | evidence_for | evidence_against |
|---|---|---|---|---|
| 1 | <concrete, falsifiable cause> | open / weakened / confirmed | <facts> | <facts> |
Current best explanation: <a concrete code location, config value, or dependency>
Next decision point: <the smallest probe or independent probe set that best splits the live hypotheses>
- A hypothesis is
confirmedonly whenevidence_foris populated ANDevidence_againsthas been checked. Noevidence_against= premature closure; keep itopen. - Ruling out every alternative does NOT confirm the survivor — it may mean all hypotheses are wrong.
The loop
- Read the ledger. Don't pre-decide which hypothesis is right.
- Run the smallest probe that changes the decision. Independent read-only probes may run together when neither depends on the other's result; record each result separately.
- Fold results back in: update
evidence_for/evidence_againstand set the next decision point. - Repeat until the causal explanation is supported. A failure may have more than one contributing confirmed cause; describe their relationship rather than forcing a single winner.
When to stop and open a spec
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.
- 9d ago First seen · 81 lines · 49 tokens per session scan A c4a8f326b434
mastermind-investigation-ledger is a skill published in the GitHub repository xcrft/mastermind (11 stars, last pushed today), licensed MIT. It adds 49 tokens to every session and 804 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 2026-08-30.
Other skills, from other repositories
roam
Codebase comprehension via roam-code CLI. Use when exploring codebases, planning modifications, debugging failures, assessing PR risk, or checking architecture health. Triggers on: understanding project structure, pre-change safety checks, finding symbols/files, blast radius analysis, affected tests, health scoring…
truecourse-fix
Fix TrueCourse violations that have suggested fixes.
trace-mcp
Use trace-mcp tools for code navigation, impact analysis, and framework-aware queries instead of Read/Grep/Glob/Bash. Activate whenever the agent needs to explore, understand, or modify a codebase that has trace-mcp indexed.
truecourse-list
List TrueCourse violations found in this repository.
lsp-inspect
Full code quality audit for a file, package, or directory. Supports batch mode (directory walk with --top ranking), comparison mode (--diff for branch-only issues), severity calibration by blast radius, fix suggestions, and confidence tiers. Applies a check taxonomy (dead symbols, silent failures, error wrapping…
lsp-dead-code
Enumerate exported symbols in a file and surface those with zero references across the workspace. Use when auditing for dead code, cleaning up APIs, or checking which exports are safe to remove.