ableton-mcp

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apply_drum_variation

Destructive

Plan or apply deterministic drum variations to an Ableton clip, using guarded confirmation, exact timing/velocity limits, accent preservation, and complete note readback.

Instructions

Plan or apply a guarded deterministic drum variation with exact native context and complete note readback.

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.
`dryRun`	No	False executes with token and hash.
`trackId`	Yes	ID from list_tracks.
`planHash`	No	Plan hash.
`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.
`confirmationToken`	No	Single-use plan token.
`expectedStateVersion`	Yes	Observed stateVersion.
`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: +[
+  {
+    "oneOf": [
+      {
+        "properties": {
+          "confirmation": {
+            "properties": {
+              "expiresAt": {
+                "type": "number"
+              },
+              "planHash": {
+                "pattern": "^[a-f0-9]{64}$",
+                "type": "string"
+              },
+              "token": {
+                "minLength": 1,
+                "type": "string"
+              }
+            },
+            "required": [
+              "token",
+              "planHash",
+              "expiresAt"
+            ],
+            "type": "object"
+          },
+          "dryRun": {
+            "const": true
+          },
+          "plan": {
+            "type": "object"
+          }
+        },
+        "required": [
+          "dryRun",
+          "plan",
+          "confirmation"
+        ],
+        "type": "object"
+      },
+      {
+        "properties": {
+          "dryRun": {
+            "const": false
+          },
+          "operationOutcome": {
+            "properties": {
+              "evidence": {
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              },
+              "reason": {
+                "type": "string"
+              },
+              "schemaVersion": {
+                "const": 1
+              },
+              "status": {
+                "enum": [
+                  "applied",
+                  "outcome_unknown",
+                  "postconditions_failed",
+                  "pending_postconditions",
+                  "pending_user_action"
+                ]
+              }
+            },
+            "required": [
+              "schemaVersion",
+              "status",
+              "reason",
+              "evidence"
+            ],
+            "type": "object"
+          }
+        },
+        "required": [
+          "dryRun",
+          "operationOutcome"
+        ],
+        "type": "object"
+      }
+    ],
+    "properties": {
+      "dryRun": {
+        "type": "boolean"
+      }
+    },
+    "required": [
+      "dryRun"
+    ],
+    "type": "object"
+  },
+  {
+    "properties": {
+      "error": {
+        "properties": {
+          "message": {
+            "type": "string"
+          },
+          "outcome": {
+            "enum": [
+              "unknown",
+              "not_executed"
+            ]
+          }
+        },
+        "required": [
+          "message",
+          "outcome"
+        ],
+        "type": "object"
+      }
+    },
+    "required": [
+      "error"
+    ],
+    "type": "object"
+  }
+]

Changed7 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 / confirmationToken / description

Previous value: -"Short-lived, single-use token returned by the matching dry run."New value: +"Single-use plan token."

changedInput schema / properties / dryRun / description

Previous value: -"Omit or true to return a plan; false requires a valid confirmationToken."New value: +"False executes with token and hash."

changedInput schema / properties / expectedStateVersion / description

Previous value: -"Exact stateVersion observed immediately before planning."New value: +"Observed stateVersion."

changedInput schema / properties / planHash / description

Previous value: -"Hash returned by the matching dry run."New value: +"Plan hash."

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

C2.8/5.0

Behavior3/5

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

Annotations already declare destructive=true, idempotent=false, readOnly=false, so safety is covered. The description adds that this is a two-phase 'plan or apply' operation and that it is 'guarded', implying state-version/token checks, but never states what gets mutated, what the guard rejects, or what 'readback' returns.

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

Conciseness4/5

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

A single front-loaded sentence with no restatement of the tool name. It is efficient, though 'exact native context and complete note readback' reads as padding that displaces more useful operational detail.

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

Completeness2/5

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

For a 15-parameter, 11-required, nested-object, destructive mutation with an output schema, this one-liner is far too thin. It omits the plan/confirm handshake mechanics (expectedStateVersion, planHash, confirmationToken), what 'guarded' protects against, and any indication of failure or partial-application behavior.

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?

At 73% schema coverage the schema documents most parameters (seed, timingAmount, velocityAmount, preserveAccentsAbove, confirmationToken, planHash, dryRun), so baseline is 3. The description adds no meaning beyond those labels and does nothing to compensate for the ~27% undocumented surface.

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

Purpose3/5

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

Names a verb+resource ('apply ... drum variation') and hints at scope ('deterministic', 'guarded'), but the qualifiers 'exact native context' and 'complete note readback' are opaque jargon. It fails to distinguish from the sibling plan_drum_variation, with which 'Plan or apply' creates overlap.

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?

No when-to-use, when-not, or prerequisite guidance. The key routing decision – dryRun plan vs. token-based apply – is left entirely to the schema, and the near-identically named sibling plan_drum_variation is never addressed.

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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