kernelCAD

Trace Outline from Image

trace_from_image

Idempotent

Use this when you need to trace a reference image into normalized waypoints. Trace pixel-space features from a reference photo into normalized [0..1] waypoints the agent can map to mm via a known scale anchor and feed to path().spline / path().nurbsSegment. Three backends are dispatched behind the scenes: opencv (deterministic; uniform-bg silhouette only), vision-llm (vision model; named points/cluttered backgrounds; needs a configured vision endpoint), and hybrid (opencv silhouette + LLM-labeled named points). Default backend is auto. Per-feature confidence is reported. Pair with the kernelcad-trace-from-image skill for the conversion-to-mm pipeline. Hosted: give the file as an https:// URL, a data: URI (base64, max 25 MB) or "asset:" from request_upload (when the file is on the user's device).

Input Schema

Name	Required	Description
`hint`	No	Optional free-text hint forwarded to vision-LLM backends (e.g. "a pair of eyewear; trace the upper brow only").
`intent`	No	The user's request in one sentence, in the user's own words and language (e.g. 'M4 bracket for a 25 mm tube, print on Bambu A1'). Helps kernelCAD improve; leave out personal data.
`priors`	No	Caller-supplied category-norm defaults (e.g. wall thickness) recorded verbatim as `assumed` ledger facts.
`backend`	No	Force a specific backend; default `auto` routes by corner-color stddev.
`features`	No	Features to trace. Defaults to a single { label: "silhouette", kind: "silhouette" } when omitted.
`imageUrl`	Yes	URL or path to the reference image. Supports file://, http(s)://, data:image/...;base64,..., or a bare filesystem path. Hosted server: pass an https:// URL, a data: URI, or "asset:<id>" from request_upload — not a path on your machine.
`validate`	No	Assumption-ledger strictness. `warn` (default) never blocks. `error` fails the call when any `missing` ledger fact (e.g. scale) is still open.
`scaleAnchor`	No	Pixel-to-real-world scale anchor: two measured points on the image. Absent -> the returned ledger's `scale` fact is `missing`.
`maxWaypointsPerFeature`	No	Cap on waypoints per feature. Defaults to 12 (suitable for medium-inflection outlines).

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 24, 2026

removedInput schema / properties / detectParts

Removed value: -{
-  "description": "Optional: use the configured vision model to detect labeled component boxes and return detectedParts plus a draftBom, normalized to the traced outline frame.",
-  "type": "boolean"
-}

Changed1 schema field changedOct 19, 2026
- addedInput schema / properties / priors / items / properties / value / type
```
Added value: +[
+  "string",
+  "number",
+  "boolean",
+  "array",
+  "object"
+]
```

Changed1 schema field changedOct 16, 2026

addedInput schema / properties / detectParts

Added value: +{
+  "description": "Optional: use the configured vision model to detect labeled component boxes and return detectedParts plus a draftBom, normalized to the traced outline frame.",
+  "type": "boolean"
+}

Changed2 schema fields changedOct 11, 2026

removedOutput schema / properties

Removed value: -{
-  "diagnostics": {
-    "items": {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    "type": "array"
-  },
-  "features": {
-    "description": "Traced features with normalized [0..1] waypoints + confidence.",
-    "items": {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    "type": "array"
-  },
-  "imageDims": {
-    "description": "Pixel dimensions [width, height] of the source image.",
-    "items": {
-      "type": "number"
-    },
-    "type": "array"
-  },
-  "ledger": {
-    "additionalProperties": true,
-    "description": "Assumption ledger: { facts, scale?, unresolvedCount } classifying every fact as visible/inferred/assumed/missing.",
-    "type": "object"
-  },
-  "ok": {
-    "type": "boolean"
-  }
-}

removedOutput schema / required

Removed value: -[
-  "ok",
-  "features",
-  "imageDims",
-  "diagnostics",
-  "ledger"
-]

Changed2 schema fields changedOct 3, 2026

changedInput schema / properties / imageUrl / description

Previous value: -"URL or path to the reference image. Supports file://, http(s)://, data:image/...;base64,..., or a bare filesystem path."New value: +"URL or path to the reference image. Supports file://, http(s)://, data:image/...;base64,..., or a bare filesystem path. Hosted server: pass an https:// URL, a data: URI, or \"asset:<id>\" from request_upload — not a path on your machine."

addedInput schema / properties / intent

Added value: +{
+  "description": "The user's request in one sentence, in the user's own words and language (e.g. 'M4 bracket for a 25 mm tube, print on Bambu A1'). Helps kernelCAD improve; leave out personal data.",
+  "maxLength": 2000,
+  "type": "string"
+}

Changed5 schema fields changedSep 21, 2026

addedInput schema / properties / priors

Added value: +{
+  "description": "Caller-supplied category-norm defaults (e.g. wall thickness) recorded verbatim as `assumed` ledger facts.",
+  "items": {
+    "properties": {
+      "confidence": {
+        "maximum": 1,
+        "minimum": 0,
+        "type": "number"
+      },
+      "id": {
+        "type": "string"
+      },
+      "statement": {
+        "type": "string"
+      },
+      "value": {}
+    },
+    "required": [
+      "id",
+      "statement",
+      "value",
+      "confidence"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedInput schema / properties / scaleAnchor

Added value: +{
+  "description": "Pixel-to-real-world scale anchor: two measured points on the image. Absent -> the returned ledger's `scale` fact is `missing`.",
+  "properties": {
+    "pixelDistance": {
+      "description": "Distance in pixels between the two measured points.",
+      "type": "number"
+    },
+    "realDistance": {
+      "description": "The same distance in real-world units.",
+      "type": "number"
+    },
+    "unit": {
+      "enum": [
+        "mm",
+        "cm",
+        "in"
+      ],
+      "type": "string"
+    }
+  },
+  "required": [
+    "pixelDistance",
+    "realDistance",
+    "unit"
+  ],
+  "type": "object"
+}

addedInput schema / properties / validate

Added value: +{
+  "description": "Assumption-ledger strictness. `warn` (default) never blocks. `error` fails the call when any `missing` ledger fact (e.g. scale) is still open.",
+  "enum": [
+    "warn",
+    "error"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / ledger

Added value: +{
+  "additionalProperties": true,
+  "description": "Assumption ledger: { facts, scale?, unresolvedCount } classifying every fact as visible/inferred/assumed/missing.",
+  "type": "object"
+}

changedOutput schema / required

Previous value: -[
-  "ok",
-  "features",
-  "imageDims",
-  "diagnostics"
-]New value: +[
+  "ok",
+  "features",
+  "imageDims",
+  "diagnostics",
+  "ledger"
+]

AddedJun 17, 2026
RemovedJun 16, 2026

Changed1 schema field changedJun 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "diagnostics": {
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "features": {
+      "description": "Traced features with normalized [0..1] waypoints + confidence.",
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "imageDims": {
+      "description": "Pixel dimensions [width, height] of the source image.",
+      "items": {
+        "type": "number"
+      },
+      "type": "array"
+    },
+    "ok": {
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "ok",
+    "features",
+    "imageDims",
+    "diagnostics"
+  ],
+  "type": "object"
+}

First observedMay 25, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the annotations: discloses backend dispatch and auto-routing by corner-color stddev, the requirement of a configured vision endpoint for vision-llm, per-feature confidence reporting, the 25 MB data-URI cap, and the consequence of omitting scaleAnchor (ledger `scale` becomes `missing`). This is exactly the operational context the annotations alone don't carry.

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?

Front-loaded with the use case, then organized by backends, confidence, skill pairing, and hosting constraints. Dense but every sentence carries information; the backend parenthetical list is slightly packed but not wasteful.

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 9 params, nested objects, an output schema, and the hosted-server deployment quirks, the description covers everything an agent needs to call it correctly: file sourcing rules, backend prerequisites, and defaults. Return values are handled by the output schema, so no gap remains.

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 already 100%, but the description still adds meaning: the hosted file-passing constraint (https/data:/asset: only, not a local path), the features default of a single silhouette, the maxWaypointsPerFeature default of 12, and how scaleAnchor drives the ledger. It could have explained validate/priors linkage more, but it earns above baseline.

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: 'trace a reference image into normalized waypoints', plus where those waypoints go (path().spline / nurbsSegment). An agent can distinguish this from siblings like draw_to_cad or mesh_to_features without opening the schema.

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?

Opens with an explicit 'Use this when…' condition and explains which backend applies to which image type (uniform-bg silhouette vs. named points/cluttered backgrounds). It doesn't name a competing sibling tool or state exclusions, so it falls short of a 5 but gives clear selection context.

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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