modularsynth-mcp

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Play notes

play_notes

Triggers scheduled MIDI note events in a live modular synth patch, controlling pitch, start time, duration, and velocity for up to 64 notes within 30 seconds.

Instructions

Play notes live, as if on the keyboard (the patch must have a MIDI→CV module wired to sound, its KEYBOARD screen set to All or Computer). Each note: MIDI pitch (60 = C4), start and duration in seconds from now, optional velocity. Up to 64 notes within 30 seconds.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "notes": "<notes>"
    },
    "name": "play_notes"
  }
}

Input Schema

Name	Required	Description	Default
`notes`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.3.1Nov 2, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already declare non-read-only, non-destructive, closed-world behavior, so the description's job is supplemental. It adds real value with the prerequisite wiring/screen settings and the hard limits (64 notes, 30 seconds), though it omits whether the call blocks during playback or what the response looks like.

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 tight sentences: purpose first, prerequisites second, note format and limits last. Every clause carries information an agent needs, with no filler.

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

Completeness4/5

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

For a scheduling-style tool with annotations covering safety and no output schema, the description covers prerequisites, timing semantics, and capacity limits. Blocking behavior and interaction with already-playing material are the remaining gaps.

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

Parameters4/5

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

Schema coverage is 0%, so the description must carry the parameter meaning, and it does: pitch with the 60 = C4 anchor, start and duration measured in seconds from now, and velocity as optional. It leaves velocity's scale and duration's 10-second cap to the schema bounds.

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

Purpose4/5

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

The description opens with a specific verb and resource ('Play notes live, as if on the keyboard'), which clearly separates immediate playback from a sibling like set_notes. It never names that sibling explicitly, so the distinction is implied rather than stated.

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

Usage Guidelines4/5

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

It gives concrete preconditions — a MIDI→CV module must be wired to sound and its KEYBOARD screen set to All or Computer — which tells the agent when this call will actually work. It stops short of naming alternatives or saying when not to use it.

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