# notation_schema

Fetch the JSON Schema (Draft 2020-12) describing the notation_render input shape. Includes every field, its type, defaults, validation rules (including the shorthand-string regex pattern), and $defs for Instrument, VoiceLine, Note, and NoteObject. WHEN TO USE: first encounter with this MCP and you want machine-readable type definitions; building a client that validates input client-side before calling notation_render; generating code (TypeScript types, Zod schemas, etc.) that consumes the format. WHEN NOT TO USE: after caching the response (stable across the v1 API); when you want learning-by-example (use notation_examples instead — worked payloads are easier to read than schema definitions). INPUT: none. Pass an empty object {}. OUTPUT (JSON): { ok: true, schema: { $schema: "https://json-schema.org/draft/2020-12/schema", $id, title, type: "object", required: ["instruments"], properties, $defs: { Instrument, VoiceLine, Note, NoteObject } }, docs: { examples, render, validate }, attribution }. The schema field is a complete JSON Schema document. EXAMPLE INPUT: {} (no parameters) TYPICAL LATENCY: 30-200 ms. Response is cached at CDN with long TTL — subsequent calls are essentially free.

Agent View of the PolicyLayer registry record for `notation_schema`. HTML page: https://policylayer.com/tools/com-gradusmusic-notation/notation-schema

## Facts

- Tool: `notation_schema`
- Server: Gradus Notation (`@gradusmusic/notation-mcp`) — https://policylayer.com/tools/com-gradusmusic-notation.md
- Install: `npx -y @gradusmusic/notation-mcp`
- Homepage: https://github.com/delmas41/gradusnotation
- Risk category: Read (Low risk)
- Registry record: grade C, 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": "notation_schema",
    "arguments": {}
  }
}
```

## Why notation_schema is rated Low

This is a pure read operation that returns metadata (a JSON Schema definition). It queries structural information about the notation_render input format without creating, modifying, executing, or deleting anything.

From the tool's own definition: "Tool name: notation_schema. Description: 'Fetch the JSON Schema...describing the notation_render input shape."

Risk signals: Bulk/mass operation — affects multiple targets

## Use case

AI agents call notation_schema to retrieve information from Gradus Notation 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 Gradus Notation:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "notation_schema": {}
  }
}
```

## Other tools on Gradus Notation (9)

- `knowledge_search` — Read — https://policylayer.com/tools/com-gradusmusic-notation/knowledge-search.md
- `notation_examples` — Read — https://policylayer.com/tools/com-gradusmusic-notation/notation-examples.md
- `notation_render` — Read — https://policylayer.com/tools/com-gradusmusic-notation/notation-render.md
- `notation_validate` — Read — https://policylayer.com/tools/com-gradusmusic-notation/notation-validate.md
- `theory_analyze_score` — Read — https://policylayer.com/tools/com-gradusmusic-notation/theory-analyze-score.md
- `theory_parse_xml` — Read — https://policylayer.com/tools/com-gradusmusic-notation/theory-parse-xml.md
- `theory_pitch_utils` — Read — https://policylayer.com/tools/com-gradusmusic-notation/theory-pitch-utils.md
- `theory_respell` — Read — https://policylayer.com/tools/com-gradusmusic-notation/theory-respell.md
- `theory_validate_ranges` — Read — https://policylayer.com/tools/com-gradusmusic-notation/theory-validate-ranges.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=com-gradusmusic-notation · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/com-gradusmusic-notation