# law.citation-check

Anti-hallucination checker for legal references. POST text to verify every cited case (CourtListener), US Code section, and CFR regulation EXISTS, with canonical metadata + source URLs. POST quotes:[{citation,quote}] to deterministically verify an attributed QUOTE actually appears in the cited opinion (ellipsis-aware) — catches fabricated quotations. Returns per-reference exists/quote-present + a summary. Checks facts (existence, quote presence), NOT whether a case legally supports a proposition.

Agent View of the PolicyLayer registry record for `law.citation-check`. HTML page: https://policylayer.com/tools/io-github-2s-io-mcp/law.citation-check

## Facts

- Tool: `law.citation-check`
- Server: Mcp (`@2sio/mcp`) — https://policylayer.com/tools/io-github-2s-io-mcp.md
- Install: `npx -y @2sio/mcp`
- Homepage: https://github.com/2s-io/sdk
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "law.citation-check",
    "arguments": {}
  }
}
```

## Why law.citation-check is rated Low

This is a read-only verification tool that queries legal databases and performs lookups without creating, modifying, or deleting data. It has no side effects beyond retrieving and comparing information. Even if an AI agent misuses it (e.g., over-queries), the blast radius is minimal—it only returns factual verification results. Low severity assigned due to benign informational purpose.

From the tool's own definition: "Tool description explicitly states it 'verify[ies]' and 'checks facts (existence, quote presence)' against external sources (CourtListener, US Code, CFR)."

Risk signals: Bulk/mass operation — affects multiple targets

## Use case

AI agents call law.citation-check to retrieve information from Mcp without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Mcp:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "law.citation-check": {}
  }
}
```

## Other tools on Mcp (571)

- `queue.ack` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/queue.ack.md
- `store.blob-delete` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/store.blob-delete.md
- `store.doc-delete` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/store.doc-delete.md
- `store.kv-delete` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/store.kv-delete.md
- `store.vector-delete` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/store.vector-delete.md
- `watchers.cancel` — Destructive — https://policylayer.com/tools/io-github-2s-io-mcp/watchers.cancel.md
- `ai.council` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/ai.council.md
- `ai.screenshot` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/ai.screenshot.md
- `batch.run` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/batch.run.md
- `dev.preflight` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/dev.preflight.md
- `dev.regex-test` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/dev.regex-test.md
- `hash.compute` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/hash.compute.md
- `pubsub.subscribe` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/pubsub.subscribe.md
- `queue.lease` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/queue.lease.md
- `search.crawl` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/search.crawl.md
- `url.render` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/url.render.md
- `watchers.crypto-address-activity` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/watchers.crypto-address-activity.md
- `watchers.earthquake` — Execute — https://policylayer.com/tools/io-github-2s-io-mcp/watchers.earthquake.md
- `predict.crypto-updown` — Financial — https://policylayer.com/tools/io-github-2s-io-mcp/predict.crypto-updown.md
- `predict.wallet` — Financial — https://policylayer.com/tools/io-github-2s-io-mcp/predict.wallet.md
- `watchers.fear-greed` — Financial — https://policylayer.com/tools/io-github-2s-io-mcp/watchers.fear-greed.md
- `watchers.fx-rate` — Financial — https://policylayer.com/tools/io-github-2s-io-mcp/watchers.fx-rate.md
- `agent.knowledge-delta` — Other — https://policylayer.com/tools/io-github-2s-io-mcp/agent.knowledge-delta.md
- `agriculture.drought` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/agriculture.drought.md
- `agriculture.stats` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/agriculture.stats.md
- `ai.chat` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/ai.chat.md
- `ai.classify` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/ai.classify.md
- `ai.describe-image` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/ai.describe-image.md
- `ai.entities` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/ai.entities.md
- `ai.extract` — Read — https://policylayer.com/tools/io-github-2s-io-mcp/ai.extract.md
- …and 541 more: https://policylayer.com/tools/io-github-2s-io-mcp.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-2s-io-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-2s-io-mcp