kernelCAD

Set Scene Return

set_scene_return

Idempotent

Use this when you need to set how the script returns its assembly. Replace the final top-level return statement with return <assembly>.model(); or return <assembly>.solvedModel(poses, options?);. Use solvedModel for mate-authored mechanisms so FK and validation run. Returns modified source plus diagnostics from re-evaluation.

Input Schema

Name	Required	Description
`code`	Yes	The .kcad.ts source code.
`mode`	Yes
`poses`	No	Optional solvedModel pose overrides keyed by mate name. Defaults to {}.
`options`	No	Optional solvedModel options such as { validate: 'warn', posesGate: 'envelope' }.
`assembly_binding`	Yes	JS identifier bound to assembly(...).

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 11, 2026

removedOutput schema / properties

Removed value: -{
-  "binding_name": {
-    "description": "JS const name bound to the new construct (when one was created).",
-    "type": "string"
-  },
-  "diagnostics": {
-    "description": "Diagnostics from re-evaluating the modified source.",
-    "items": {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    "type": "array"
-  },
-  "error": {
-    "description": "Failure message (present when ok is false).",
-    "type": "string"
-  },
-  "new_code": {
-    "description": "Modified .kcad.ts source (present on success). Caller persists it.",
-    "type": "string"
-  },
-  "ok": {
-    "description": "Whether the edit applied and re-evaluated cleanly.",
-    "type": "boolean"
-  }
-}

removedOutput schema / required
```
Removed value: -[
-  "ok"
-]
```

Changed1 schema field changedJun 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "binding_name": {
+      "description": "JS const name bound to the new construct (when one was created).",
+      "type": "string"
+    },
+    "diagnostics": {
+      "description": "Diagnostics from re-evaluating the modified source.",
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "error": {
+      "description": "Failure message (present when ok is false).",
+      "type": "string"
+    },
+    "new_code": {
+      "description": "Modified .kcad.ts source (present on success). Caller persists it.",
+      "type": "string"
+    },
+    "ok": {
+      "description": "Whether the edit applied and re-evaluated cleanly.",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "ok"
+  ],
+  "type": "object"
+}

AddedJun 13, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond annotations, it discloses the exact mutation made to source code, the difference in behavior between model and solvedModel, and that the result includes modified source plus diagnostics from re-evaluation.

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 three compact sentences, front-loads the use case, then gives the exact transformation and mode guidance. Every sentence adds useful information.

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?

For a source-mutating tool with five parameters, an output schema, and annotations, the description covers purpose, replacement behavior, mode selection, and result format sufficiently for an agent to invoke it correctly.

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 high at 80%, so the schema already documents most parameters. The description adds meaningful semantic guidance for mode, especially why solvedModel may be needed for mate-authored mechanisms.

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 states a specific verb and resource: setting how the script returns its assembly by replacing the final top-level return statement. The exact code transformation makes it clearly distinguishable from general evaluation or repair tools.

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?

It gives clear usage context and explicitly recommends solvedModel for mate-authored mechanisms so FK and validation run. However, it does not name a sibling tool alternative or state when not to use this tool.

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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