# notation_validate

Pre-flight validate a notation_render input without rendering. Returns errors with concrete fix field that tells the agent exactly how to repair malformed input. Substantially cheaper than notation_render because it skips the Verovio engraving step entirely. WHEN TO USE: when iterating on input shape and uncertain whether it is well-formed; when input came from user-supplied or LLM-generated data that may be malformed; when surfacing precise validation errors to your end user before committing to a full render; when learning the input format (combine with notation_examples to see canonical inputs). WHEN NOT TO USE: if input is known to be valid (just call notation_render directly — it validates internally too); if you have not learned the schema yet (call notation_schema or notation_examples first to see the format). INPUT: identical shape to notation_render. instruments array required (each with name and notes or voices). OUTPUT (JSON, valid): { ok: true, requestId, valid: true, warnings: ValidationIssue[], meta: { measureCount, instrumentCount, voiceCount, durationBeats }, attribution }. Warnings are non-blocking notices (e.g. unusual time signature handling). OUTPUT (JSON, invalid): { ok: false, requestId, valid: false, errors: ValidationIssue[], warnings, attribution }. Each ValidationIssue: { path: "instruments[0].voices[0].notes[3]", code: "BAD_PITCH"|"BAD_DURATION"|"MISSING_FIELD"|"BAD_KEY_SIG"|..., message, fix: "Use scientific notation: letter A-G + optional # or b + octave number, e.g. C4, F#5, Bb3.", severity: "error"|"warning" }. Surface the fix to your user or use it to auto-repair. EXAMPLE INPUT: { "instruments": [{ "name": "Violin", "notes": ["C5/q","D5/q","E5/q","F5/q"] }] } TYPICAL LATENCY: 30-100 ms (no Verovio render; pure JSON-to-Score conversion + bar-line arithmetic).

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

## Facts

- Tool: `notation_validate`
- 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: 6 (1 required)
- Recommended policy verdict: Allowed

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `tempo` | number | no |  |
| `title` | string | no |  |
| `composer` | string | no |  |
| `instruments` | array | yes | Same shape as notation_render. See notation_schema for the full JSON Schema. |
| `keySignature` | string | no |  |
| `timeSignature` | array | no |  |

Parameters from the server's own tool schema.

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

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "notation_validate",
    "arguments": {
      "instruments": []
    }
  }
}
```

## Why notation_validate is rated Low

This tool purely validates input and returns diagnostic information (errors and fixes). It has no side effects—it does not modify data, execute external operations, delete anything, or commit financial obligations. It is a read-like operation that queries the structure and validity of notation input, making it the safest category.

From the tool's own definition: "Tool performs pre-flight validation without rendering or modifying data. Description states it 'Pre-flight validate a notation_render input without rendering' and 'Returns errors with concrete fix field'."

## Use case

AI agents call notation_validate 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_validate": {}
  }
}
```

## 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_schema` — Read — https://policylayer.com/tools/com-gradusmusic-notation/notation-schema.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