ableton-mcp

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set_simpler_sample_region

Destructive

Sets a loaded Simpler's playback start/end markers in native sample frames, including nested racks. Requires stopped transport and an inactive, unarmed single-sample target; does not crop audio.

Instructions

Set a loaded Simpler playback region in native sample frames, including nested racks. At least one marker; omitted bound stays unchanged. Requires stopped transport and an inactive unarmed single-sample target. Binds native context and verifies exact markers; does not crop the source file. Partial failure requires inspection; no automatic rollback. All profile.

Input Schema

Name	Required	Description
`dryRun`	No	False executes with token and hash.
`trackId`	Yes	ID from list_tracks.
`deviceId`	Yes	ID from list_devices.
`planHash`	No	Plan hash.
`endMarkerFrames`	No	Native end frame, above start and below observed lengthFrames. Omit to retain observed end.
`confirmationToken`	No	Single-use plan token.
`startMarkerFrames`	No	Native start frame, below end. Omit to retain observed start.
`expectedStateVersion`	Yes	Observed stateVersion.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.3.1Oct 23, 2026

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"
+  }
+]

Addedv0.3.0Oct 19, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Adds behavior beyond the annotations: it does not crop the source file, it binds native context and verifies exact markers, and failures are partial with no automatic rollback. The non-atomic, no-rollback failure mode is exactly the kind of trait annotations (destructiveHint=true) cannot express.

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?

Dense and front-loaded: purpose first, then constraints, then behavioral caveats, with no filler sentences. The telegraphic style ('All profile.') is efficient, though slightly terse in places.

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 destructive, 8-parameter mutation with an output schema, the description covers preconditions, marker constraints, non-cropping behavior, and failure handling. Return values are covered by the output schema, so nothing critical is missing.

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 description coverage is 100%, so the schema already documents all 8 parameters, including the omit-to-retain semantics. The description's 'omitted bound stays unchanged' merely restates what startMarkerFrames/endMarkerFrames already say, adding no new syntax or format detail.

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 (Set) and resource (Simpler playback region) plus scope (native sample frames, nested racks). An agent can tell what it does, but it never references the adjacent sibling set_simpler_manual_slices, so sibling differentiation is left implicit.

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?

Provides concrete preconditions for use — stopped transport, inactive unarmed single-sample target — and a validity rule (at least one marker). It does not name an alternative tool or an explicit 'do not use when', so it stops short of full routing 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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