diff --git a/services/mcp-server/src/modules/support/debug-pack.ts b/services/mcp-server/src/modules/support/debug-pack.ts
index 1dc01c68..a21d961a 100644
--- a/services/mcp-server/src/modules/support/debug-pack.ts
+++ b/services/mcp-server/src/modules/support/debug-pack.ts
@@ -1,6 +1,10 @@
 import { z } from 'zod';
 import { registerTool } from '../tools/registry.js';
-import { telemetryClusters, diagnosticsCreateSession } from '../../lib/platform-client.js';
+import {
+  telemetryClusters,
+  diagnosticsCreateSession,
+  type TelemetryCluster,
+} from '../../lib/platform-client.js';
 import type { McpToolRequest } from '../tools/types.js';
 
 const tokenOf = (req: McpToolRequest) => req.headers.authorization?.slice(7);
@@ -41,7 +45,7 @@ registerTool({
     const generatedAt = new Date().toISOString();
 
     // Step 1: collect error clusters
-    let clusters: import('../../lib/platform-client.js').TelemetryCluster[] = [];
+    let clusters: TelemetryCluster[] = [];
     let clusterError: string | undefined;
     try {
       const result = await telemetryClusters({ from: args.from, to: args.to }, opts);
diff --git a/services/mcp-server/src/modules/tools/registry.test.ts b/services/mcp-server/src/modules/tools/registry.test.ts
index 67f63758..d31a1f1f 100644
--- a/services/mcp-server/src/modules/tools/registry.test.ts
+++ b/services/mcp-server/src/modules/tools/registry.test.ts
@@ -30,6 +30,39 @@ describe('tool registry', () => {
   it('getTool returns undefined for unknown tool', () => {
     expect(getTool('does.not.exist')).toBeUndefined();
   });
+
+  it('zodToJsonSchema emits correct types for boolean/number/array fields', () => {
+    registerTool({
+      name: 'test.types',
+      description: 'Type test',
+      requiredRole: 'viewer',
+      inputSchema: z.object({
+        flag: z.boolean(),
+        count: z.coerce.number(),
+        tags: z.array(z.string()),
+        label: z.string().optional(),
+        enabled: z.boolean().default(false),
+      }),
+      async execute(args) {
+        return args;
+      },
+    });
+    const tool = listTools().find(t => t.name === 'test.types');
+    const props = (tool?.inputSchema as { properties: Record<string, { type: string }> })
+      .properties;
+    expect(props.flag.type).toBe('boolean');
+    expect(props.count.type).toBe('number');
+    expect(props.tags.type).toBe('array');
+    expect(props.label.type).toBe('string');
+    // ZodDefault should unwrap to boolean, not 'string'
+    expect(props.enabled.type).toBe('boolean');
+    // optional + default fields should NOT be in required
+    const required = tool?.inputSchema.required as string[];
+    expect(required).toContain('flag');
+    expect(required).toContain('count');
+    expect(required).not.toContain('label');
+    expect(required).not.toContain('enabled');
+  });
 });
 
 describe('tool execute', () => {
diff --git a/services/mcp-server/src/modules/tools/registry.ts b/services/mcp-server/src/modules/tools/registry.ts
index 9709f67e..a864faf0 100644
--- a/services/mcp-server/src/modules/tools/registry.ts
+++ b/services/mcp-server/src/modules/tools/registry.ts
@@ -20,31 +20,26 @@ export function listTools(): McpToolMeta[] {
   }));
 }
 
+type ZodDef = {
+  typeName: string;
+  description?: string;
+  innerType?: { _def: ZodDef };
+  shape?: () => Record<string, ZodTypeAny>;
+};
+
 /** Minimal Zod → JSON Schema converter (object shapes only — sufficient for tool docs) */
 function zodToJsonSchema(schema: ZodTypeAny): Record<string, unknown> {
   try {
-    const def = (
-      schema as unknown as { _def: { typeName: string; shape?: () => Record<string, ZodTypeAny> } }
-    )._def;
+    const def = (schema as unknown as { _def: ZodDef })._def;
     if (def.typeName === 'ZodObject' && def.shape) {
       const shape = def.shape();
       const properties: Record<string, unknown> = {};
       const required: string[] = [];
       for (const [key, field] of Object.entries(shape)) {
-        const fieldDef = (
-          field as unknown as {
-            _def: {
-              typeName: string;
-              description?: string;
-              innerType?: { _def: { typeName: string } };
-            };
-          }
-        )._def;
-        const isOptional = fieldDef.typeName === 'ZodOptional';
-        const innerTypeName = isOptional ? fieldDef.innerType?._def.typeName : fieldDef.typeName;
-        const jsonType = zodTypeNameToJsonType(innerTypeName ?? '');
-        properties[key] = { type: jsonType, description: fieldDef.description ?? key };
-        if (!isOptional) required.push(key);
+        const fieldDef = (field as unknown as { _def: ZodDef })._def;
+        const { resolvedType, isRequired, description } = resolveZodDef(fieldDef);
+        properties[key] = { ...resolvedType, description: description ?? key };
+        if (isRequired) required.push(key);
       }
       return { type: 'object', properties, required };
     }
@@ -54,9 +49,48 @@ function zodToJsonSchema(schema: ZodTypeAny): Record<string, unknown> {
   return { type: 'object' };
 }
 
-function zodTypeNameToJsonType(typeName: string): string {
-  if (typeName === 'ZodNumber' || typeName === 'ZodCoerce') return 'number';
-  if (typeName === 'ZodBoolean') return 'boolean';
-  if (typeName === 'ZodArray') return 'array';
-  return 'string'; // ZodString, ZodEnum, ZodLiteral, unknown
+/**
+ * Unwrap ZodOptional / ZodDefault wrappers and resolve the JSON type for a field.
+ * Returns the JSON Schema fragment plus whether the field is required.
+ */
+function resolveZodDef(def: ZodDef): {
+  resolvedType: Record<string, unknown>;
+  isRequired: boolean;
+  description?: string;
+} {
+  const description = def.description;
+  if (def.typeName === 'ZodOptional') {
+    const inner = def.innerType?._def;
+    return {
+      resolvedType: inner ? zodDefToJsonType(inner) : { type: 'string' },
+      isRequired: false,
+      description,
+    };
+  }
+  if (def.typeName === 'ZodDefault') {
+    const inner = def.innerType?._def;
+    return {
+      resolvedType: inner ? zodDefToJsonType(inner) : { type: 'string' },
+      isRequired: false, // has default → not required in JSON Schema
+      description,
+    };
+  }
+  return { resolvedType: zodDefToJsonType(def), isRequired: true, description };
+}
+
+function zodDefToJsonType(def: ZodDef): Record<string, unknown> {
+  switch (def.typeName) {
+    case 'ZodObject':
+      return { type: 'object' };
+    case 'ZodArray':
+      return { type: 'array' };
+    case 'ZodBoolean':
+      return { type: 'boolean' };
+    case 'ZodNumber':
+      return { type: 'number' };
+    case 'ZodEnum':
+      return { type: 'string' };
+    default:
+      return { type: 'string' };
+  }
 }