lilypond-mcp

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Engrave LilyPond Code

engrave_code

Idempotent

Engrave inline LilyPond code without a source file, generating preview PNGs, PDFs, SVGs, or EPS so you can iterate on a musical idea and adjust it immediately.

Instructions

Engrave LilyPond code passed inline, without needing a source file on disk. Useful for iterating on a musical idea: engrave, read the preview PNG, adjust, repeat. For anything worth keeping, write a .ly file and use engrave_file instead.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`code`	Yes	LilyPond source code, e.g. '\version "2.26.0" { c\' e\' g\' }'
`crop`	No	Crop assets to the music itself (required for EPS)
`name`	No	Basename for the generated assets	snippet
`formats`	No	Asset formats to generate; png is handy while iterating on a snippet
`preview`	No	Attach the preview PNG to the result as an image, so the engraving is visible inline without reading a file. Turn off for batch runs.
`output_dir`	No	Directory the generated assets are written to (created if missing)	build
`include_dirs`	No	Directories searched by \include, e.g. a shared settings library

Output Schema

TableJSON Schema

Name	Required	Description
`ok`	Yes
`errors`	No
`outputs`	Yes
`previewPng`	No	Cropped PNG of the engraved music — read this file to inspect the result

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.2.1Aug 28, 2026

addedInput schema / properties / preview

Added value: +{
+  "default": true,
+  "description": "Attach the preview PNG to the result as an image, so the engraving is visible inline without reading a file. Turn off for batch runs.",
+  "type": "boolean"
+}

First observedv0.1.0Aug 25, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare the safety profile (readOnlyHint false, idempotentHint true, destructiveHint false). The description adds useful behavioral context — that it engraves from an in-memory string, that a preview PNG comes back for iteration, and that it is not the persistence path. It does not itself state that assets are written to a directory, but the schema and annotations cover that.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the core capability, then the iteration workflow, then the hand-off to the sibling. Zero filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present and 100% parameter coverage, the description need not restate outputs. It supplies the workflow and sibling routing an agent needs to pick this tool correctly, and nothing material is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and every parameter (crop, name, formats, preview, output_dir, include_dirs) is documented in the schema, so the baseline is 3. The description echoes the preview workflow but adds no syntax or format semantics beyond what the schema already provides.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Engrave LilyPond code') and immediately differentiates scope: inline code with no source file on disk. This cleanly separates it from the sibling engrave_file, which requires a .ly file.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit when-to-use ('iterating on a musical idea: engrave, read the preview PNG, adjust, repeat') and an explicit when-not-to + alternative ('For anything worth keeping, write a .ly file and use engrave_file instead'). This is textbook routing guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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