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 agentmods add skills/jakevin/fastcontext-agent-tools/fastcontext-explorernpx skills add Jakevin/fastcontext-agent-tools --skill fastcontext-explorergit clone --depth 1 https://github.com/Jakevin/fastcontext-agent-toolsWrote 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/jakevin/fastcontext-agent-tools/fastcontext-explorer)<a href="https://agentmods.dev/skills/jakevin/fastcontext-agent-tools/fastcontext-explorer"><img src="https://agentmods.dev/badge/skills/jakevin/fastcontext-agent-tools/fastcontext-explorer.svg" alt="Measured on agentmods" 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 | $0.00130 | $0.00832 |
| Opus 5 | $0.00065 | $0.00416 |
| Sonnet 5 | $0.00026 | $0.00166 |
| Haiku 4.5 | $0.00013 | $0.00083 |
Grade A, and why
fastcontext-explorer 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 4d 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 — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FastContext Explorer
Workflow
- Check availability first with the MCP tool
fastcontext_health. - If health is usable, call
fastcontext_explorewith a specific query and the repository root. - Treat returned citations as candidate evidence, not proof. Read the cited files and line ranges yourself before editing or answering.
- If citations are sparse, off-target, or missing, refine the query once with concrete terms from the task, error, subsystem, or nearby filenames.
- For debugging poor searches, use
fastcontext_explore_with_traceand inspect the saved trajectory.
When to Use
- Understand unfamiliar code before editing, reviewing, debugging, or explaining it.
- Trace logic across layers, such as request to handler to service to storage.
- Answer code questions like "How does X work?", "Where is Y defined?", or "What calls Z?".
- Map what a symbol depends on or what depends on it.
- Assess which files are likely affected by a change.
When unsure and the answer needs more than one file, run FastContext first.
When Not to Use
- You already read the exact file and surrounding context in this session.
- One known file and one obvious search will answer the question.
- The task is pure writing or generation with no repository exploration.
- The task is non-code.
Query Shape
Write concise exploration requests that name behavior and intent:
Find where OAuth access tokens are refreshed and which tests cover expired token handling.
Prefer subsystem and failure language over generic searches:
Locate the request validation path that rejects oversized uploaded files.
Avoid asking FastContext to solve or patch:
Fix the upload bug.
MCP Tools
Use fastcontext_explore:
{
"repo_path": "/absolute/path/to/repo",
"query": "Locate the request validation path that rejects oversized uploaded files.",
"max_turns": 6,
"citation": true
}
Use fastcontext_explore_with_trace when a trajectory is needed:
What ships with it
2 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.
- 4d ago First seen · 102 lines · 130 tokens per session scan A a1c37b0273e5
fastcontext-explorer is a skill published in the GitHub repository Jakevin/fastcontext-agent-tools (19 stars, last pushed 2mo ago), licensed MIT. It adds 130 tokens to every session and 832 once invoked, about $0.0006 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.
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