diff --git a/extensions/canvas/src/tool-schema.ts b/extensions/canvas/src/tool-schema.ts
index 0af9387046ec..10475384240c 100644
--- a/extensions/canvas/src/tool-schema.ts
+++ b/extensions/canvas/src/tool-schema.ts
@@ -1,3 +1,9 @@
+import {
+  optionalFiniteNumberSchema,
+  optionalNonNegativeIntegerSchema,
+  optionalPositiveIntegerSchema,
+  stringEnum,
+} from "openclaw/plugin-sdk/channel-actions";
 import { Type } from "typebox";
 
 export const CANVAS_ACTIONS = [
@@ -12,30 +18,23 @@ export const CANVAS_ACTIONS = [
 
 export const CANVAS_SNAPSHOT_FORMATS = ["png", "jpg", "jpeg"] as const;
 
-function stringEnum<T extends readonly string[]>(values: T) {
-  return Type.Unsafe<T[number]>({
-    type: "string",
-    enum: [...values],
-  });
-}
-
 export const CanvasToolSchema = Type.Object({
   action: stringEnum(CANVAS_ACTIONS),
   gatewayUrl: Type.Optional(Type.String()),
   gatewayToken: Type.Optional(Type.String()),
-  timeoutMs: Type.Optional(Type.Number()),
+  timeoutMs: optionalPositiveIntegerSchema(),
   node: Type.Optional(Type.String()),
   target: Type.Optional(Type.String()),
-  x: Type.Optional(Type.Number()),
-  y: Type.Optional(Type.Number()),
-  width: Type.Optional(Type.Number()),
-  height: Type.Optional(Type.Number()),
+  x: optionalFiniteNumberSchema(),
+  y: optionalFiniteNumberSchema(),
+  width: optionalFiniteNumberSchema(),
+  height: optionalFiniteNumberSchema(),
   url: Type.Optional(Type.String()),
   javaScript: Type.Optional(Type.String()),
   outputFormat: Type.Optional(stringEnum(CANVAS_SNAPSHOT_FORMATS)),
-  maxWidth: Type.Optional(Type.Number()),
-  quality: Type.Optional(Type.Number()),
-  delayMs: Type.Optional(Type.Number()),
+  maxWidth: optionalPositiveIntegerSchema(),
+  quality: optionalFiniteNumberSchema({ minimum: 0, maximum: 1 }),
+  delayMs: optionalNonNegativeIntegerSchema(),
   jsonl: Type.Optional(Type.String()),
   jsonlPath: Type.Optional(Type.String()),
 });
diff --git a/extensions/canvas/src/tool.test.ts b/extensions/canvas/src/tool.test.ts
index 0da45934a3d0..38b9e137fe8b 100644
--- a/extensions/canvas/src/tool.test.ts
+++ b/extensions/canvas/src/tool.test.ts
@@ -97,6 +97,72 @@ describe("Canvas tool", () => {
     expect(imageResultParams?.imageSanitization).toEqual({ maxDimensionPx: 1600 });
   });
 
+  it("normalizes numeric string params before invoking node canvas commands", async () => {
+    mocks.callGatewayTool.mockResolvedValue({
+      payload: {
+        format: "png",
+        base64: Buffer.from("not-a-real-png").toString("base64"),
+      },
+    });
+    const tool = createCanvasTool();
+
+    await tool.execute("tool-call-1", {
+      action: "present",
+      timeoutMs: "1500",
+      x: "10.5",
+      y: "-2",
+      width: "640",
+      height: "480",
+    });
+
+    expect(mocks.callGatewayTool).toHaveBeenLastCalledWith(
+      "node.invoke",
+      { timeoutMs: 1500 },
+      expect.objectContaining({
+        command: "canvas.present",
+        params: {
+          placement: {
+            x: 10.5,
+            y: -2,
+            width: 640,
+            height: 480,
+          },
+        },
+      }),
+    );
+
+    await tool.execute("tool-call-2", {
+      action: "snapshot",
+      maxWidth: "800",
+      quality: "0.75",
+    });
+
+    expect(mocks.callGatewayTool).toHaveBeenLastCalledWith(
+      "node.invoke",
+      {},
+      expect.objectContaining({
+        command: "canvas.snapshot",
+        params: {
+          format: "png",
+          maxWidth: 800,
+          quality: 0.75,
+        },
+      }),
+    );
+  });
+
+  it("rejects malformed numeric canvas params before invoking node commands", async () => {
+    const tool = createCanvasTool();
+
+    await expect(
+      tool.execute("tool-call-1", {
+        action: "snapshot",
+        maxWidth: "800px",
+      }),
+    ).rejects.toThrow("maxWidth must be a positive integer");
+    expect(mocks.callGatewayTool).not.toHaveBeenCalled();
+  });
+
   it("rejects node-controlled snapshot formats before creating image results", async () => {
     mocks.callGatewayTool.mockResolvedValue({
       payload: {
diff --git a/extensions/canvas/src/tool.ts b/extensions/canvas/src/tool.ts
index b19752c99f6a..b4d096ea89db 100644
--- a/extensions/canvas/src/tool.ts
+++ b/extensions/canvas/src/tool.ts
@@ -11,6 +11,7 @@ import {
   jsonResult,
   readStringParam,
 } from "openclaw/plugin-sdk/channel-actions";
+import { readFiniteNumberParam, readPositiveIntegerParam } from "openclaw/plugin-sdk/param-readers";
 import type { AnyAgentTool, OpenClawConfig } from "openclaw/plugin-sdk/plugin-entry";
 import { resolvePreferredOpenClawTmpDir } from "openclaw/plugin-sdk/temp-path";
 import { normalizeCanvasSnapshotFileExtension, parseCanvasSnapshotPayload } from "./cli-helpers.js";
@@ -29,7 +30,7 @@ function readGatewayCallOptions(params: Record<string, unknown>) {
   return {
     gatewayUrl: readStringParam(params, "gatewayUrl", { trim: false }),
     gatewayToken: readStringParam(params, "gatewayToken", { trim: false }),
-    timeoutMs: typeof params.timeoutMs === "number" ? params.timeoutMs : undefined,
+    timeoutMs: readPositiveIntegerParam(params, "timeoutMs"),
   };
 }
 
@@ -114,10 +115,10 @@ export function createCanvasTool(options?: CanvasToolOptions): AnyAgentTool {
       switch (action) {
         case "present": {
           const placement = {
-            x: typeof params.x === "number" ? params.x : undefined,
-            y: typeof params.y === "number" ? params.y : undefined,
-            width: typeof params.width === "number" ? params.width : undefined,
-            height: typeof params.height === "number" ? params.height : undefined,
+            x: readFiniteNumberParam(params, "x"),
+            y: readFiniteNumberParam(params, "y"),
+            width: readFiniteNumberParam(params, "width"),
+            height: readFiniteNumberParam(params, "height"),
           };
           const invokeParams: Record<string, unknown> = {};
           const presentTarget =
@@ -169,14 +170,11 @@ export function createCanvasTool(options?: CanvasToolOptions): AnyAgentTool {
               ? params.outputFormat.trim().toLowerCase()
               : "png";
           const format = formatRaw === "jpg" || formatRaw === "jpeg" ? "jpeg" : "png";
-          const maxWidth =
-            typeof params.maxWidth === "number" && Number.isFinite(params.maxWidth)
-              ? params.maxWidth
-              : undefined;
-          const quality =
-            typeof params.quality === "number" && Number.isFinite(params.quality)
-              ? params.quality
-              : undefined;
+          const maxWidth = readPositiveIntegerParam(params, "maxWidth");
+          const quality = readFiniteNumberParam(params, "quality", {
+            min: 0,
+            max: 1,
+          });
           const raw = (await invoke("canvas.snapshot", {
             format,
             maxWidth,