Claude Code Plugins Directory is a marketplace containing plugins for Claude Code, including tools, commands, skills, agents, hooks, and model context servers. Claude Code users browse it to install Anthropic-maintained or approved third-party extensions.
Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add anthropics/claude-plugins-official/plugin install math-proofWrote 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/anthropics/claude-plugins-official/siege)<a href="https://agentmods.dev/skills/anthropics/claude-plugins-official/siege"><img src="https://agentmods.dev/badge/skills/anthropics/claude-plugins-official/siege/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/anthropics/claude-plugins-official/siege"><img src="https://agentmods.dev/badge/skills/anthropics/claude-plugins-official/siege.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00107 | $0.18238 |
| Opus 5.5 | $0.00043 | $0.07295 |
| Sonnet 5.5 | $0.00021 | $0.03648 |
| Haiku 4.5 | $0.00011 | $0.01824 |
Grade A, and why
siege 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 15d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- siege — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 733 lines — stays where its author put it; the contents beside it link to each section on GitHub.
math-proof: siege
The approach
The skill works on one problem in at most MAX_ROUNDS rounds. Each round a judge writes a few self-contained questions, at most WAVE of them before round ESC_ROUND. The steps below call them queries. Each question goes to a fresh worker that sees only that question and the problem statement. The judge reads the answers, rewrites the running summary, and adds to a ledger of claims marked PROVED, REFUTED or OPEN. One claim is the goal, set in round 1; the judge may set a new goal at a later round, and in particular may raise it to a more significant statement once it is proved (the proved goal then stays in the ledger as the fallback result, to which the judge returns if two waves bring the raised goal no nearer; when the goal is raised you tell the user and copy the proved result to DIR/result-so-far.md). When an answer holds a complete written proof or disproof of the goal, two more workers check that exact text line by line. Once both pass, the judge concludes or raises the goal. Before round MIN_ROUNDS, that is the only way to conclude. From round ESC_ROUND on, if no complete proof or disproof is in hand, a round may hold up to WAVE_DEEP questions for higher-effort workers. All but at most two of them aim at the one statement still missing from the proof. After the rounds end, the judge writes a self-contained proof.md, a worker checks it, and the judge finalizes it. Unless the goal the run ends on was both proved and checked twice during the rounds, there are also extra revision passes and a last wave of full proof attempts before finalizing. proof.md has a Status section that says plainly what is and is not proved. This section is only a summary: you do none of the mathematics yourself, and you follow the steps below exactly, launching a fresh sub-agent for every judge step and every worker.
You are the ORCHESTRATOR of this protocol. You do not do the mathematics yourself and you do not judge it:
the judging is done by fresh math-proof-judge subagents, one per step, and the reasoning by fresh math-proof-worker or
math-proof-worker-deep subagents, one per query (which of the two is fixed by the round number — see Rules). Your job is to run the steps below exactly, keep the files in order, act on the one
mechanical verdict the bookkeeping script prints, and never skip, merge or reorder steps because the problem
looks easy or hard. Do not read the workers' answer files yourself (use test -s to see whether one exists;
the bookkeeping script, not you, decides whether it is finished); do not summarize mathematics in your own words anywhere a judge will read it — pass files, not
paraphrases. Work unattended to the end: there is nobody to answer questions.
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.
- 15d ago First seen · 733 lines · 107 tokens per session scan A f40134d3b418
siege is a skill published in the GitHub repository anthropics/claude-plugins-official (39,070 stars, last pushed today), licensed Apache-2.0. It adds 107 tokens to every session and 18,238 once invoked, about $0.0004 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 2026-10-01.
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