diff --git a/client/pr_demo.mp4 b/client/pr_demo.mp4
deleted file mode 100644
index b6ae523d5..000000000
Binary files a/client/pr_demo.mp4 and /dev/null differ
diff --git a/client/src/App.tsx b/client/src/App.tsx
index 6c9ae3331..04794df05 100644
--- a/client/src/App.tsx
+++ b/client/src/App.tsx
@@ -22,6 +22,8 @@ import { SESSION_KEYS, getServerSpecificKey } from "./lib/constants";
 import { AuthDebuggerState, EMPTY_DEBUGGER_STATE } from "./lib/auth-types";
 import { OAuthStateMachine } from "./lib/oauth-state-machine";
 import { cacheToolOutputSchemas } from "./utils/schemaUtils";
+import { cleanParams } from "./utils/paramUtils";
+import type { JsonSchemaType } from "./utils/jsonUtils";
 import React, {
   Suspense,
   useCallback,
@@ -777,12 +779,18 @@ const App = () => {
     lastToolCallOriginTabRef.current = currentTabRef.current;
 
     try {
+      // Find the tool schema to clean parameters properly
+      const tool = tools.find((t) => t.name === name);
+      const cleanedParams = tool?.inputSchema
+        ? cleanParams(params, tool.inputSchema as JsonSchemaType)
+        : params;
+
       const response = await sendMCPRequest(
         {
           method: "tools/call" as const,
           params: {
             name,
-            arguments: params,
+            arguments: cleanedParams,
             _meta: {
               progressToken: progressTokenRef.current++,
             },
@@ -793,6 +801,8 @@ const App = () => {
       );
 
       setToolResult(response);
+      // Clear any validation errors since tool execution completed
+      setErrors((prev) => ({ ...prev, tools: null }));
     } catch (e) {
       const toolResult: CompatibilityCallToolResult = {
         content: [
@@ -804,6 +814,8 @@ const App = () => {
         isError: true,
       };
       setToolResult(toolResult);
+      // Clear validation errors - tool execution errors are shown in ToolResults
+      setErrors((prev) => ({ ...prev, tools: null }));
     }
   };
 
diff --git a/client/src/components/ToolsTab.tsx b/client/src/components/ToolsTab.tsx
index 31979f0da..0123296af 100644
--- a/client/src/components/ToolsTab.tsx
+++ b/client/src/components/ToolsTab.tsx
@@ -131,14 +131,15 @@ const ToolsTab = ({
             </h3>
           </div>
           <div className="p-4">
-            {error ? (
-              <Alert variant="destructive">
-                <AlertCircle className="h-4 w-4" />
-                <AlertTitle>Error</AlertTitle>
-                <AlertDescription>{error}</AlertDescription>
-              </Alert>
-            ) : selectedTool ? (
+            {selectedTool ? (
               <div className="space-y-4">
+                {error && (
+                  <Alert variant="destructive">
+                    <AlertCircle className="h-4 w-4" />
+                    <AlertTitle>Error</AlertTitle>
+                    <AlertDescription>{error}</AlertDescription>
+                  </Alert>
+                )}
                 <p className="text-sm text-gray-600 dark:text-gray-400">
                   {selectedTool.description}
                 </p>
@@ -184,16 +185,27 @@ const ToolsTab = ({
                             id={key}
                             name={key}
                             placeholder={prop.description}
-                            value={(params[key] as string) ?? ""}
-                            onChange={(e) =>
-                              setParams({
-                                ...params,
-                                [key]:
-                                  e.target.value === ""
-                                    ? undefined
-                                    : e.target.value,
-                              })
+                            value={
+                              params[key] === undefined
+                                ? ""
+                                : String(params[key])
                             }
+                            onChange={(e) => {
+                              const value = e.target.value;
+                              if (value === "") {
+                                // Field cleared - set to undefined
+                                setParams({
+                                  ...params,
+                                  [key]: undefined,
+                                });
+                              } else {
+                                // Field has value - keep as string
+                                setParams({
+                                  ...params,
+                                  [key]: value,
+                                });
+                              }
+                            }}
                             className="mt-1"
                           />
                         ) : prop.type === "object" || prop.type === "array" ? (
@@ -227,13 +239,35 @@ const ToolsTab = ({
                             id={key}
                             name={key}
                             placeholder={prop.description}
-                            value={(params[key] as string) ?? ""}
+                            value={
+                              params[key] === undefined
+                                ? ""
+                                : String(params[key])
+                            }
                             onChange={(e) => {
                               const value = e.target.value;
-                              setParams({
-                                ...params,
-                                [key]: value === "" ? "" : Number(value),
-                              });
+                              if (value === "") {
+                                // Field cleared - set to undefined
+                                setParams({
+                                  ...params,
+                                  [key]: undefined,
+                                });
+                              } else {
+                                // Field has value - try to convert to number, but store input either way
+                                const num = Number(value);
+                                if (!isNaN(num)) {
+                                  setParams({
+                                    ...params,
+                                    [key]: num,
+                                  });
+                                } else {
+                                  // Store invalid input as string - let server validate
+                                  setParams({
+                                    ...params,
+                                    [key]: value,
+                                  });
+                                }
+                              }
                             }}
                             className="mt-1"
                           />
diff --git a/client/src/components/__tests__/ToolsTab.test.tsx b/client/src/components/__tests__/ToolsTab.test.tsx
index 290605dd8..a50f62df3 100644
--- a/client/src/components/__tests__/ToolsTab.test.tsx
+++ b/client/src/components/__tests__/ToolsTab.test.tsx
@@ -644,6 +644,7 @@ describe("ToolsTab", () => {
       description: "Tool with JSON parameters",
       inputSchema: {
         type: "object" as const,
+        required: ["config", "data"], // Make them required so they render as form fields
         properties: {
           config: {
             type: "object" as const,
@@ -693,15 +694,16 @@ describe("ToolsTab", () => {
         callTool: mockCallTool,
       });
 
-      // Find JSON editor textareas
+      // Find JSON editor textareas (should have one for each required field: config and data)
       const textareas = screen.getAllByRole("textbox");
+      expect(textareas.length).toBe(2);
 
-      // Enter valid JSON in the first textarea
+      // Enter valid JSON in each textarea
       fireEvent.change(textareas[0], {
-        target: {
-          value:
-            '{ "config": { "setting": "value" }, "data": ["item1", "item2"] }',
-        },
+        target: { value: '{ "setting": "value" }' },
+      });
+      fireEvent.change(textareas[1], {
+        target: { value: '["item1", "item2"]' },
       });
 
       // Wait for debounced updates
@@ -799,9 +801,16 @@ describe("ToolsTab", () => {
       });
 
       const textareas = screen.getAllByRole("textbox");
+      expect(textareas.length).toBe(2);
+
+      // Clear both textareas (empty JSON should be valid)
+      fireEvent.change(textareas[0], { target: { value: "{}" } });
+      fireEvent.change(textareas[1], { target: { value: "[]" } });
 
-      // Clear the textarea (empty JSON should be valid)
-      fireEvent.change(textareas[0], { target: { value: "" } });
+      // Wait for debounced updates
+      await act(async () => {
+        await new Promise((resolve) => setTimeout(resolve, 350));
+      });
 
       // Try to run the tool
       const runButton = screen.getByRole("button", { name: /run tool/i });
diff --git a/client/src/utils/__tests__/paramUtils.test.ts b/client/src/utils/__tests__/paramUtils.test.ts
new file mode 100644
index 000000000..3dfd53828
--- /dev/null
+++ b/client/src/utils/__tests__/paramUtils.test.ts
@@ -0,0 +1,208 @@
+import { cleanParams } from "../paramUtils";
+import type { JsonSchemaType } from "../jsonUtils";
+
+describe("cleanParams", () => {
+  it("should preserve required fields even when undefined", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: ["requiredString", "requiredNumber"],
+      properties: {
+        requiredString: { type: "string" },
+        requiredNumber: { type: "number" },
+        optionalString: { type: "string" },
+        optionalNumber: { type: "number" },
+      },
+    };
+
+    const params = {
+      requiredString: undefined,
+      requiredNumber: undefined,
+      optionalString: undefined,
+      optionalNumber: undefined,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({
+      requiredString: undefined,
+      requiredNumber: undefined,
+      // optionalString and optionalNumber should be omitted
+    });
+  });
+
+  it("should omit optional fields with empty strings", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: [],
+      properties: {
+        optionalString: { type: "string" },
+        optionalNumber: { type: "number" },
+      },
+    };
+
+    const params = {
+      optionalString: "",
+      optionalNumber: "",
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({});
+  });
+
+  it("should omit optional fields with undefined values", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: [],
+      properties: {
+        optionalString: { type: "string" },
+        optionalNumber: { type: "number" },
+      },
+    };
+
+    const params = {
+      optionalString: undefined,
+      optionalNumber: undefined,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({});
+  });
+
+  it("should omit optional fields with null values", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: [],
+      properties: {
+        optionalString: { type: "string" },
+        optionalNumber: { type: "number" },
+      },
+    };
+
+    const params = {
+      optionalString: null,
+      optionalNumber: null,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({});
+  });
+
+  it("should preserve optional fields with meaningful values", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: [],
+      properties: {
+        optionalString: { type: "string" },
+        optionalNumber: { type: "number" },
+        optionalBoolean: { type: "boolean" },
+      },
+    };
+
+    const params = {
+      optionalString: "hello",
+      optionalNumber: 42,
+      optionalBoolean: false, // false is a meaningful value
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({
+      optionalString: "hello",
+      optionalNumber: 42,
+      optionalBoolean: false,
+    });
+  });
+
+  it("should handle mixed required and optional fields", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: ["requiredField"],
+      properties: {
+        requiredField: { type: "string" },
+        optionalWithValue: { type: "string" },
+        optionalEmpty: { type: "string" },
+        optionalUndefined: { type: "number" },
+      },
+    };
+
+    const params = {
+      requiredField: "",
+      optionalWithValue: "test",
+      optionalEmpty: "",
+      optionalUndefined: undefined,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({
+      requiredField: "",
+      optionalWithValue: "test",
+    });
+  });
+
+  it("should handle schema without required array", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      properties: {
+        field1: { type: "string" },
+        field2: { type: "number" },
+      },
+    };
+
+    const params = {
+      field1: "",
+      field2: undefined,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({});
+  });
+
+  it("should preserve zero values for numbers", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: [],
+      properties: {
+        optionalNumber: { type: "number" },
+      },
+    };
+
+    const params = {
+      optionalNumber: 0,
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({
+      optionalNumber: 0,
+    });
+  });
+
+  it("should handle the new undefined-first approach (no empty strings)", () => {
+    const schema: JsonSchemaType = {
+      type: "object",
+      required: ["requiredField"],
+      properties: {
+        requiredField: { type: "string" },
+        optionalField: { type: "string" },
+      },
+    };
+
+    // New behavior: cleared fields are undefined, never empty strings
+    const params = {
+      requiredField: undefined, // cleared required field
+      optionalField: undefined, // cleared optional field
+    };
+
+    const cleaned = cleanParams(params, schema);
+
+    expect(cleaned).toEqual({
+      requiredField: undefined, // required field preserved as undefined
+      // optionalField omitted entirely
+    });
+  });
+});
diff --git a/client/src/utils/paramUtils.ts b/client/src/utils/paramUtils.ts
new file mode 100644
index 000000000..dfc418023
--- /dev/null
+++ b/client/src/utils/paramUtils.ts
@@ -0,0 +1,34 @@
+import type { JsonSchemaType } from "./jsonUtils";
+
+/**
+ * Cleans parameters by removing undefined, null, and empty string values for optional fields
+ * while preserving all values for required fields.
+ *
+ * @param params - The parameters object to clean
+ * @param schema - The JSON schema defining which fields are required
+ * @returns Cleaned parameters object with optional empty fields omitted
+ */
+export function cleanParams(
+  params: Record<string, unknown>,
+  schema: JsonSchemaType,
+): Record<string, unknown> {
+  const cleaned: Record<string, unknown> = {};
+  const required = schema.required || [];
+
+  for (const [key, value] of Object.entries(params)) {
+    const isFieldRequired = required.includes(key);
+
+    if (isFieldRequired) {
+      // Required fields: always include, even if empty string or falsy
+      cleaned[key] = value;
+    } else {
+      // Optional fields: only include if they have meaningful values
+      if (value !== undefined && value !== "" && value !== null) {
+        cleaned[key] = value;
+      }
+      // Empty strings, undefined, null for optional fields → omit completely
+    }
+  }
+
+  return cleaned;
+}