Morpha

Set group window

set_group_window

Destructive

TRIM a group's own visible window — the [start, start+duration) range over which the group and its subtree are drawn. The contents are NOT moved or deleted: this clips what is shown, so use it to hide the head or tail of a whole section. Writing a window overrides the group's derived contents-hull from then on. Two safety corrections apply automatically: the group's OWN keyframes are compensated for the change in start so its animation doesn't jump (reported as keyframesCompensatedBy), and the duration is grown if needed so the window can never hide one of the group's own authored keyframes (reported as grownToCoverKeyframes). To MOVE the group and its contents instead, use shift_group.

Input Schema

TableJSON Schema

Name	Required	Description
`start`	Yes	First frame the group is drawn on, in its parent timeline (0-indexed, 30 fps).
`duration`	Yes	How many frames the group stays drawn for (≥ 1). Grown automatically if it would hide the group's own keyframes.
`elementId`	Yes	The group's id (group.<id> or the bare <id>).
`projectId`	Yes	Opaque project id (a v4 UUID, from list_projects/create_project). Selects which existing project this call mutates.

Output Schema

TableJSON Schema

Name	Required	Description
`ok`	Yes	Whether the call succeeded.
`data`	No	The payload, shaped by the tool.
`note`	No	What to do next when not ready.
`error`	No	Why it failed.
`status`	No	For cache-backed readers: whether the answer was ready.
`editorUrl`	No	Opens this project in the editor.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 17, 2026

removedInput schema / properties / anonymousToken

Removed value: -{
-  "description": "The token create_anonymous_account returned. This connection has no Morpha key, so every call carries it.",
-  "type": "string"
-}

changedInput schema / required

Previous value: -[
-  "elementId",
-  "start",
-  "duration",
-  "projectId",
-  "anonymousToken"
-]New value: +[
+  "elementId",
+  "start",
+  "duration",
+  "projectId"
+]

Changed1 schema field changedSep 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "description": "The result envelope every Morpha tool returns.",
+  "properties": {
+    "data": {
+      "description": "The payload, shaped by the tool.",
+      "type": [
+        "object",
+        "array",
+        "string",
+        "number",
+        "boolean",
+        "null"
+      ]
+    },
+    "editorUrl": {
+      "description": "Opens this project in the editor.",
+      "type": "string"
+    },
+    "error": {
+      "description": "Why it failed.",
+      "type": "string"
+    },
+    "note": {
+      "description": "What to do next when not ready.",
+      "type": "string"
+    },
+    "ok": {
+      "description": "Whether the call succeeded.",
+      "type": "boolean"
+    },
+    "status": {
+      "description": "For cache-backed readers: whether the answer was ready.",
+      "enum": [
+        "ready",
+        "not-ready"
+      ],
+      "type": "string"
+    }
+  },
+  "required": [
+    "ok"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedSep 11, 2026

addedInput schema / properties / anonymousToken

Added value: +{
+  "description": "The token create_anonymous_account returned. This connection has no Morpha key, so every call carries it.",
+  "type": "string"
+}

changedInput schema / required

Previous value: -[
-  "elementId",
-  "start",
-  "duration",
-  "projectId"
-]New value: +[
+  "elementId",
+  "start",
+  "duration",
+  "projectId",
+  "anonymousToken"
+]

First observedSep 7, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations already declare destructiveHint=true, but the description adds substantial nuance: it clarifies that contents are not moved or deleted, only clipped. It discloses that writing a window overrides the derived contents-hull, and explains two automatic safety corrections (keyframesCompensatedBy and grownToCoverKeyframes). This goes far beyond the annotation and provides rich behavioral context for a destructive operation.

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?

The description is concise despite covering multiple aspects: purpose, effect, safety corrections, and alternative. It is front-loaded with the core action ('TRIM a group's own visible window') and efficiently packages all essential information in three sentences. No word is wasted.

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 the complexity of a destructive window-setting operation, the description covers all necessary context: what the window is, what it does to contents, how safety corrections work, what gets reported, and the alternative for moving. It also mentions the output fields (keyframesCompensatedBy and grownToCoverKeyframes), and since an output schema exists, return details are likely covered there. The description is complete for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds value by explaining that duration is automatically grown to avoid hiding keyframes and that start compensation affects keyframes. It also clarifies that the window is [start, start+duration) and that it's in the parent timeline at 30 fps, which the schema already mentions. The added nuance about safety corrections exceeds the schema's parameter descriptions.

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

Purpose5/5

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

The description clearly states the tool trims a group's visible window, defining the exact range and effect (clips what is shown, not moved/deleted). It distinguishes from shift_group, which moves contents, and mentions the sibling explicitly. The verb 'TRIM' and resource 'group' are specific and unambiguous.

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

Usage Guidelines5/5

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

The description explicitly says when to use it: 'use it to hide the head or tail of a whole section.' It also provides a clear alternative: 'To MOVE the group and its contents instead, use shift_group.' This gives both positive and negative guidance, leaving no ambiguity about when this tool is appropriate.

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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