diff --git a/client/src/components/ToolsTab.tsx b/client/src/components/ToolsTab.tsx
index 9d3dca70..cd8e2ad5 100644
--- a/client/src/components/ToolsTab.tsx
+++ b/client/src/components/ToolsTab.tsx
@@ -159,17 +159,21 @@ 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;
-                              if (value === "" && !required) {
-                                // Optional field cleared - set to undefined to omit from request
+                              if (value === "") {
+                                // Field cleared - set to undefined
                                 setParams({
                                   ...params,
                                   [key]: undefined,
                                 });
                               } else {
-                                // Field has value or is required - keep as string
+                                // Field has value - keep as string
                                 setParams({
                                   ...params,
                                   [key]: value,
@@ -206,22 +210,26 @@ 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;
-                              if (value === "" && !required) {
-                                // Optional field cleared - set to undefined to omit from request
+                              if (value === "") {
+                                // Field cleared - set to undefined
                                 setParams({
                                   ...params,
                                   [key]: undefined,
                                 });
                               } else {
-                                // Field has value or is required - convert to number
+                                // Field has value - convert to number (never store strings)
                                 const num = Number(value);
-                                if (!isNaN(num) || value === "") {
+                                if (!isNaN(num)) {
                                   setParams({
                                     ...params,
-                                    [key]: value === "" ? "" : num,
+                                    [key]: num,
                                   });
                                 }
                               }
diff --git a/client/src/utils/__tests__/paramUtils.test.ts b/client/src/utils/__tests__/paramUtils.test.ts
index 84735a04..3dfd5382 100644
--- a/client/src/utils/__tests__/paramUtils.test.ts
+++ b/client/src/utils/__tests__/paramUtils.test.ts
@@ -2,7 +2,7 @@ import { cleanParams } from "../paramUtils";
 import type { JsonSchemaType } from "../jsonUtils";
 
 describe("cleanParams", () => {
-  it("should preserve required fields even when empty", () => {
+  it("should preserve required fields even when undefined", () => {
     const schema: JsonSchemaType = {
       type: "object",
       required: ["requiredString", "requiredNumber"],
@@ -15,17 +15,17 @@ describe("cleanParams", () => {
     };
 
     const params = {
-      requiredString: "",
-      requiredNumber: 0,
-      optionalString: "",
+      requiredString: undefined,
+      requiredNumber: undefined,
+      optionalString: undefined,
       optionalNumber: undefined,
     };
 
     const cleaned = cleanParams(params, schema);
 
     expect(cleaned).toEqual({
-      requiredString: "",
-      requiredNumber: 0,
+      requiredString: undefined,
+      requiredNumber: undefined,
       // optionalString and optionalNumber should be omitted
     });
   });
@@ -181,4 +181,28 @@ describe("cleanParams", () => {
       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
+    });
+  });
 });