ableton-mcp

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plan_drum_variation

Read-onlyIdempotent

Plan deterministic, bounded drum timing and velocity humanization plus an optional final-bar fill, preserving unrelated notes and rejecting collisions.

Instructions

Plan deterministic bounded timing and velocity humanization plus an optional explicit final-bar fill. Preserves unrelated notes and rejects collisions.

Input Schema

Name	Required	Description
`bars`	Yes
`fill`	No
`grid`	Yes
`seed`	Yes	Deterministic variation seed.
`clipId`	Yes	list_clips Session ID or supported list_arrangement_clips ID.
`trackId`	Yes	ID from list_tracks.
`startBar`	Yes
`laneNotes`	Yes	Unique drum pitches to humanize.
`timingAmount`	Yes	Maximum timing movement as a fraction of the selected grid step.
`velocityAmount`	Yes	Maximum velocity movement.
`preserveAccentsAbove`	Yes	Required threshold; do not alter velocity at or above it.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv0.3.1Oct 23, 2026

changedInput schema / properties / clipId / description

Previous value: -"Session ID from list_clips; Arrangement ID from list_arrangement_clips where supported."New value: +"list_clips Session ID or supported list_arrangement_clips ID."

removedOutput schema / additionalProperties
```
Removed value: -true
```

addedOutput schema / anyOf

Added value: +[
+  {
+    "properties": {
+      "before": {
+        "type": "object"
+      },
+      "clipTiming": {
+        "type": "object"
+      },
+      "gridReference": {
+        "type": "object"
+      },
+      "stateVersion": {
+        "minimum": 1,
+        "type": "integer"
+      },
+      "variation": {
+        "type": "object"
+      }
+    },
+    "required": [
+      "stateVersion",
+      "gridReference",
+      "clipTiming",
+      "before",
+      "variation"
+    ],
+    "type": "object"
+  },
+  {
+    "properties": {
+      "error": {
+        "properties": {
+          "message": {
+            "type": "string"
+          },
+          "outcome": {
+            "enum": [
+              "unknown",
+              "not_executed"
+            ]
+          }
+        },
+        "required": [
+          "message",
+          "outcome"
+        ],
+        "type": "object"
+      }
+    },
+    "required": [
+      "error"
+    ],
+    "type": "object"
+  }
+]

Changed3 schema fields changedv0.3.0Oct 19, 2026

changedInput schema / properties / clipId / description

Previous value: -"Stable clip ID: track-N:clip-M from list_clips, or track-N:arrangement-clip-M from list_arrangement_clips for tools that support Arrangement clips."New value: +"Session ID from list_clips; Arrangement ID from list_arrangement_clips where supported."

changedInput schema / properties / trackId / description

Previous value: -"Stable track ID returned by list_tracks."New value: +"ID from list_tracks."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "type": "object"
+}

First observedv0.1.0Sep 23, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, but the description adds real behavioral context beyond them: 'deterministic' (reinforcing reproducibility), 'bounded' movement, that unrelated notes are preserved, and that collisions are rejected as a failure mode. That preservation/rejection contract is genuinely useful and not derivable from the structured fields.

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?

Two tightly packed sentences with zero filler; the core action is front-loaded and the behavioral contract (preserve/reject) follows. Every clause carries information.

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?

Given that an output schema exists (return values need no explanation) and annotations plus a nested schema carry the structural detail, the description supplies the remaining behavioral essentials: determinism, bounding, note preservation, and collision rejection. What remains (per-param detail, plan-vs-apply routing) is a minor gap against an already rich structured surface.

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 64%, so the description should add some param meaning, and it does conceptually map timingAmount/velocityAmount ('bounded timing and velocity'), seed ('deterministic'), and the nested fill object. However it leaves grid, laneNotes, startBar, bars, and preserveAccentsAbove unexplained, so it only partially compensates for the coverage gap.

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 states a specific verb ('Plan') and a precise resource (deterministic bounded timing and velocity humanization plus an optional final-bar fill), so an agent can tell what the tool produces. It does not explicitly contrast with close siblings such as apply_drum_variation or plan_midi_humanization, so it falls short of full sibling differentiation.

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

Usage Guidelines2/5

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

There is no statement of when to use this vs alternatives; the 'plan vs apply' relationship with the sibling apply_drum_variation is left to inference. The only usage hint is that the fill is optional, which is closer to schema framing than 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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