Morpha

Set track loop

set_track_loop

Destructive

Set the extrapolation mode for one property's animation track. Modes: "hold" (default — holds the boundary keyframe's value past the ends), "loop" (wraps frames past the last keyframe back to the first, restarting the animation), "ping-pong" (alternates direction each cycle, bouncing back and forth), "cycle" (wraps like loop but each cycle adds the boundary delta — used for endless rotation or scrolling). Has no effect on tracks with fewer than 2 keyframes.

Input Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes
`property`	Yes
`elementId`	Yes	Layer id (video/image/shape/group).
`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",
-  "property",
-  "mode",
-  "projectId",
-  "anonymousToken"
-]New value: +[
+  "elementId",
+  "property",
+  "mode",
+  "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",
-  "property",
-  "mode",
-  "projectId"
-]New value: +[
+  "elementId",
+  "property",
+  "mode",
+  "projectId",
+  "anonymousToken"
+]

First observedSep 7, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already indicate this is a destructive, read-write operation, so the description's job is to add nuance. It does this well by explaining what each mode does and by disclosing the no-effect condition for short tracks. This gives an agent a realistic model of the tool's behavior beyond the raw mutation flag.

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?

Every sentence earns its place: the first defines the operation, the second explains all four mode options, and the third gives an important limitation. It is front-loaded with the primary action and remains compact despite covering a fair amount of behavior.

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 tool with an output schema and four parameters, the description plus input schema covers the required calling context well: projectId and elementId are in the schema, mode semantics are in the description, and the keyframe-count caveat addresses a real edge case. It loses a point only for not distinguishing itself from the sibling set_loop tool.

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 only 50%, with 'mode' and 'property' lacking descriptions. The description compensates strongly for 'mode' by explaining each enum value's behavior, turning raw strings into actionable semantics. It offers less for 'property' and the ID parameters, though those are adequately covered by the schema or self-explanatory.

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?

States a specific verb and resource: 'Set the extrapolation mode for one property's animation track.' This clearly distinguishes it from broader tools like set_loop by narrowing scope to a single property's track. The enumeration of modes further clarifies exactly what the tool does.

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

Usage Guidelines3/5

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

The description gives useful context, such as the default mode being 'hold' and the caveat that it 'has no effect on tracks with fewer than 2 keyframes.' However, it never explicitly addresses when to use this tool versus the similarly named sibling set_loop, nor does it mention any explicit exclusions or alternatives beyond the keyframe count.

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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