investigate

investigate is a skill for Claude Code from MadAppGang/magus. It costs 43 tokens per session (2,091 once invoked), scanned A, original, MIT.

A guided method for investigating code, with separate paths for bugs, missing tests, architecture and implementation questions. It chooses a path from the wording of the request and searches the relevant code relationships in sequence.

In plain words
What is it for?
Use it to debug failures, find test gaps, understand how code is structured, trace data flow, or follow callers and dependencies around an implementation.
Why use it?
It prevents a code investigation from starting with the wrong questions or stopping after only one result. It makes the chosen approach visible so it can be corrected early.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents.

Part of the code-analysis plugin — 3 skills, 3 commands, 1 agent, 1 hook shipped together

Good fit Use it to debug failures, find test gaps, understand how code is structured, trace data flow, or follow callers and dependencies around an implementation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/madappgang/magus/investigate
Install

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.

Any agent
npx skills add MadAppGang/magus --skill investigate
Clone the repo
git clone --depth 1 https://github.com/MadAppGang/magus

Made for: Claude Code.

Or install code-analysis, the plugin that ships this one along with the rest of its 3 skills, 3 commands, 1 agent, 1 hook.

Wrote 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.

agentmods badge for investigate

README.md
[![agentmods](https://agentmods.dev/badge/skills/madappgang/magus/investigate/github.svg)](https://agentmods.dev/skills/madappgang/magus/investigate)
Your own site
<a href="https://agentmods.dev/skills/madappgang/magus/investigate"><img src="https://agentmods.dev/badge/skills/madappgang/magus/investigate/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.

agentmods 80×15 button for investigate

Your own site · 80×15
<a href="https://agentmods.dev/skills/madappgang/magus/investigate"><img src="https://agentmods.dev/badge/skills/madappgang/magus/investigate.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,091 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00043 $0.02091
Opus 5 $0.00022 $0.01045
Sonnet 5 $0.00009 $0.00418
Haiku 4.5 $0.00004 $0.00209

Measured 12d ago against content hash cc65e525505d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

investigate 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 12d 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.

plugins/code-analysis/skills/investigate/SKILL.md · 208 lines

How it starts

The opening of the file, as written. The whole thing — 208 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Investigate

One investigation, one mode. Pick the mode from the request, announce it, then run that mode's sequence. The retrieval mechanics live in the code-search skill; this skill is about which questions to ask and in what order.

Routing

Mode Trigger keywords Question sequence
Bug debug, error, broken, failing, crash full context → inbound → outbound → transitive impact
Test gap test, coverage, edge case, mock inbound filtered to test files → gap detection
Architecture architecture, design, structure, layer structural map → centrality → dependency closure
Implementation (default) how does, implementation, data flow locate → inbound → outbound → full context

Collision order: Bug > Test > Architecture > Implementation. No keyword matches → Implementation.

Announce the routing before executing it — print the query, the chosen mode, and the one-line reason. A wrong route is then correctable in one turn instead of after the investigation is spent.

Discipline that applies to every mode

  • Never rank-truncate a result set. Ranking already put the important results first; cutting by line count deletes them. Narrow with scope instead.
  • An error and an empty result look alike and mean opposite things. Establish which one you have before you report either.
  • Name the method behind every finding. Lexical search is the right tool for exact strings, counts and filename patterns — using it is routing, not a fallback. Using it without saying so is the defect.
  • Blocked, never stalled. A subagent has no tool for asking the user a question. If you cannot proceed, do not wait for an answer that cannot arrive and do not decide on the user's behalf: return a result beginning BLOCKED: naming what is missing and what would unblock it, and let the dispatching orchestrator ask.
  • Centrality is relative. Treat it as tiers — core, key, ordinary, leaf — never as a number to threshold. An absent centrality means unknown, not low.

Read the full file on GitHub · 208 lines

Changes

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.

  1. 12d ago First seen · 208 lines · 43 tokens per session scan A cc65e525505d

Subscribe to this mod's changes

investigate is a skill published in the GitHub repository MadAppGang/magus (9 stars, last pushed yesterday), licensed MIT. It adds 43 tokens to every session and 2,091 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 2026-08-31.

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