Morpha

Set matte source

set_matte_source

Destructive

Set (or clear) a track matte — the host shows only where the matte source is opaque. The HOST can be a leaf (image., video., shapes., text.) OR a group. (a group is a layer of sorts): a group host clips ALL its composited children to the source shape's path — e.g. a marching chevron strip + black backing shown only inside an arrow / band shape. For a leaf host the source can be any leaf (use a text. source for video-/image-filled letterforms); for a group host the source must be a shape (shapes.). The source is CONSUMED: it stops painting as a layer of its own, so do NOT hide it or set its opacity to 0 (an invisible stencil empties the mask and the host vanishes). It has no time window of its own: it follows the host's, and attaching drops its block and edge transitions (source_window_dropped in the result). Its position, scale, rotation and keyframes shape the mask. Pass null to clear.

Input Schema

TableJSON Schema

Name	Required	Description
`elementId`	Yes	Host being masked: image/video/shapes/text.<id>, or group.<id>.
`projectId`	Yes	Opaque project id (a v4 UUID, from list_projects/create_project). Selects which existing project this call mutates.
`matte_inverted`	No	Optional. Invert the mask (knock-out): the host shows everywhere EXCEPT where the source is opaque — a punch-through / spotlight. Honored on leaf hosts; ignored on group hosts. Omitted = preserve current; clearing the mask resets it.
`matte_source_id`	Yes	Element id of the layer whose alpha drives the mask, or null to clear.

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",
-  "matte_source_id",
-  "projectId",
-  "anonymousToken"
-]New value: +[
+  "elementId",
+  "matte_source_id",
+  "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",
-  "matte_source_id",
-  "projectId"
-]New value: +[
+  "elementId",
+  "matte_source_id",
+  "projectId",
+  "anonymousToken"
+]

First observedSep 7, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Goes well beyond the destructiveHint annotation by disclosing that the source is consumed, that hiding/opacity-0 will empty the mask, that the source follows the host's time window, and that attaching drops block/edge transitions. This is exactly the kind of behavioral context an agent needs to avoid destructive mistakes.

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 long but every sentence carries nontrivial guidance: purpose, host/source compatibility, consumption warning, masking behavior, and clearing. It front-loads the core definition before diving into constraints and edge cases.

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 the tool and the presence of an output schema, the description covers all needed operational details: valid inputs, restrictions, side effects, transform behavior, time-window handling, and the clear path. No critical gap remains for correct invocation.

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

Parameters5/5

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

Schema coverage is 100%, yet the description still adds substantial parameter-level meaning: elementId's host type rules, matte_source_id's consumption behavior and null-to-clear, matte_inverted's leaf-only support and reset behavior, plus transform inheritance. This far exceeds the baseline for high schema coverage.

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?

Description uses a specific verb ('Set (or clear)') and resource ('track matte'), and explains the host/matte relationship with concrete examples. It fully distinguishes this operation from the many sibling set_* tools by naming its object (matte source) and its effect.

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 extensive context on when and how to use: valid host types (leaf vs group), valid source types, the requirement that group hosts use shapes, and the caution that the source is consumed. It doesn't explicitly name alternative tools, but the constraints are clear enough that an agent can apply it correctly.

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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