ableton-mcp

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plan_midi_chord_arpeggiation

Read-onlyIdempotent

Generate deterministic up, down, up-down, or seeded-random arpeggiation of complete chord onsets in Ableton MIDI clips using step spacing, gate length, and random seed.

Instructions

Plan deterministic up, down, up-down, or seeded-random arpeggiation of complete chord onsets.

Input Schema

Name	Required	Description
`gate`	Yes	Note duration as a fraction of stepBeats.
`mode`	Yes	Pitch traversal order for each complete chord onset.
`seed`	Yes	Deterministic seed used by random mode.
`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.
`stepBeats`	Yes	Spacing between arpeggiated notes in beats.

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

B3.2/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safe, non-mutating profile is covered. The description adds that output is deterministic and scoped to 'complete chord onsets', which is useful context, but it doesn't explain what planning produces or how it relates to the apply step.

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 wasted words. It is efficient, though its terseness is arguably part of why usage context is thin.

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?

An output schema exists, so return values need no explanation, and the schema fully covers parameters. However, for a planning tool in a family with clear plan/apply pairs, the description omits how this fits the workflow or what it feeds into, leaving an agent to infer the planning-vs-application distinction.

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%, so all seven parameters are already documented, including mode values and the 'fraction of stepBeats' semantics of gate. The description adds the mode names and the 'complete chord onsets' constraint but no syntax beyond the schema, so the 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?

The description states a specific verb (plan) and resource (arpeggiation of complete chord onsets) and enumerates the four modes. It could differentiate from the sibling apply_midi_chord_arpeggiation or other plan_midi_* tools, but the core purpose is clear.

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 when-to-use, when-not, or prerequisite guidance. It never mentions the apply_midi_chord_arpeggiation counterpart or what conditions call for planning vs applying. Usage is only loosely implied by the name.

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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