ableton-mcp

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plan_midi_chord_doubling

Read-onlyIdempotent

Plans exact bass, top, or outer octave chord doublings across selected MIDI note onsets, specifying how the lowest and highest voices move.

Instructions

Plan exact bass, top, or outer octave chord doublings across complete selected onsets.

Input Schema

Name	Required	Description
`mode`	Yes	Add the lowest voice down an octave, highest voice up an octave, or both outer voices.
`clipId`	Yes	list_clips Session ID or supported list_arrangement_clips ID.
`noteIds`	Yes	Unique stable note IDs at complete chord onsets.
`trackId`	Yes	ID from list_tracks.

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": {
+      "clipId": {
+        "type": "string"
+      },
+      "context": {
+        "type": "object"
+      },
+      "plan": {
+        "properties": {
+          "changes": {
+            "items": {
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "newNotes": {
+            "items": {
+              "properties": {
+                "duration": {
+                  "type": "number"
+                },
+                "pitch": {
+                  "maximum": 127,
+                  "minimum": 0,
+                  "type": "integer"
+                },
+                "start": {
+                  "type": "number"
+                },
+                "velocity": {
+                  "maximum": 127,
+                  "minimum": 0,
+                  "type": "integer"
+                }
+              },
+              "required": [
+                "pitch",
+                "start",
+                "duration",
+                "velocity"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "noteIds": {
+            "items": {
+              "type": "integer"
+            },
+            "type": "array"
+          },
+          "notes": {
+            "items": {
+              "properties": {
+                "duration": {
+                  "type": "number"
+                },
+                "pitch": {
+                  "maximum": 127,
+                  "minimum": 0,
+                  "type": "integer"
+                },
+                "start": {
+                  "type": "number"
+                },
+                "velocity": {
+                  "maximum": 127,
+                  "minimum": 0,
+                  "type": "integer"
+                }
+              },
+              "required": [
+                "pitch",
+                "start",
+                "duration",
+                "velocity"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "preservedNotes": {
+            "items": {
+              "type": "object"
+            },
+            "type": "array"
+          }
+        },
+        "required": [],
+        "type": "object"
+      },
+      "stateVersion": {
+        "minimum": 1,
+        "type": "integer"
+      },
+      "trackId": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "stateVersion",
+      "trackId",
+      "clipId",
+      "context",
+      "plan"
+    ],
+    "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

B3.3/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered structurally. The description adds one real behavioral detail — that onsets must be complete chords — but says nothing about what a 'plan' is, whether it is persisted, or how it is later applied.

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?

A single front-loaded sentence with no filler; the voice options are enumerated inline rather than spread across a paragraph.

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

Completeness3/5

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

With an output schema present and annotations covering safety, the description is adequate for invocation. The missing piece is the plan-to-apply lifecycle, which matters for an agent choosing between the two doubling tools.

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 the mode enum is fully documented with per-value semantics, so the schema carries the load. The description's mention of bass/top/outer mirrors the enum rather than adding new meaning, so baseline 3 applies.

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?

States a specific verb (Plan) and resource (octave chord doublings) and enumerates the voice options (bass, top, outer), which cleanly separates it from inversion/drop-voicing siblings. It does not, however, distinguish itself from the near-identical apply_midi_chord_doubling, leaving the plan-vs-apply split to inference.

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 explicit when-to-use guidance and no mention of the apply_midi_chord_doubling sibling that presumably consumes the plan. The only usage signal is the embedded constraint 'complete selected onsets', which hints at a precondition but is not framed as 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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