diff --git a/packages/api/src/tools/definitions.spec.ts b/packages/api/src/tools/definitions.spec.ts
index 4dc1acdf83..139fdfac3a 100644
--- a/packages/api/src/tools/definitions.spec.ts
+++ b/packages/api/src/tools/definitions.spec.ts
@@ -553,6 +553,78 @@ describe('definitions.ts', () => {
         expect(toolDef.name).toBe('list_items_mcp_my-server');
         expect((toolDef as { serverName?: string }).serverName).toBe('my-server');
       });
+
+      it('should convert empty MCP tool descriptions to undefined', async () => {
+        const mockServerTools = {
+          no_desc_tool_mcp_asana: {
+            function: {
+              name: 'no_desc_tool_mcp_asana',
+              description: '',
+              parameters: { type: 'object', properties: {} },
+            },
+          },
+          has_desc_tool_mcp_asana: {
+            function: {
+              name: 'has_desc_tool_mcp_asana',
+              description: 'List tasks',
+              parameters: { type: 'object', properties: {} },
+            },
+          },
+        };
+
+        mockGetOrFetchMCPServerTools.mockResolvedValue(mockServerTools);
+
+        const params: LoadToolDefinitionsParams = {
+          userId: 'user-123',
+          agentId: 'agent-123',
+          tools: ['sys__all__sys_mcp_asana'],
+        };
+
+        const deps: LoadToolDefinitionsDeps = {
+          getOrFetchMCPServerTools: mockGetOrFetchMCPServerTools,
+          isBuiltInTool: mockIsBuiltInTool,
+        };
+
+        const result = await loadToolDefinitions(params, deps);
+
+        const noDef = result.toolDefinitions.find((d) => d.name === 'no_desc_tool_mcp_asana');
+        expect(noDef).toBeDefined();
+        expect(noDef?.description).toBeUndefined();
+
+        const hasDef = result.toolDefinitions.find((d) => d.name === 'has_desc_tool_mcp_asana');
+        expect(hasDef).toBeDefined();
+        expect(hasDef?.description).toBe('List tasks');
+      });
+
+      it('should convert empty description to undefined for directly named MCP tool', async () => {
+        const toolName = 'no_desc_tool_mcp_asana';
+        mockGetOrFetchMCPServerTools.mockResolvedValue({
+          [toolName]: {
+            function: {
+              name: toolName,
+              description: '',
+              parameters: { type: 'object', properties: {} },
+            },
+          },
+        });
+
+        const params: LoadToolDefinitionsParams = {
+          userId: 'user-123',
+          agentId: 'agent-123',
+          tools: [toolName],
+        };
+
+        const deps: LoadToolDefinitionsDeps = {
+          getOrFetchMCPServerTools: mockGetOrFetchMCPServerTools,
+          isBuiltInTool: mockIsBuiltInTool,
+        };
+
+        const result = await loadToolDefinitions(params, deps);
+
+        const def = result.toolDefinitions.find((d) => d.name === toolName);
+        expect(def).toBeDefined();
+        expect(def?.description).toBeUndefined();
+      });
     });
 
     describe('toolkit expansion', () => {
diff --git a/packages/api/src/tools/definitions.ts b/packages/api/src/tools/definitions.ts
index 7f82bc06ec..bdb501e9d3 100644
--- a/packages/api/src/tools/definitions.ts
+++ b/packages/api/src/tools/definitions.ts
@@ -158,7 +158,7 @@ export async function loadToolDefinitions(
         if (toolDef?.function) {
           mcpToolDefs.push({
             name: actualToolName,
-            description: toolDef.function.description,
+            description: toolDef.function.description || undefined,
             parameters: toolDef.function.parameters
               ? normalizeJsonSchema(resolveJsonSchemaRefs(toolDef.function.parameters))
               : undefined,
@@ -173,7 +173,7 @@ export async function loadToolDefinitions(
     if (toolDef?.function) {
       mcpToolDefs.push({
         name: toolName,
-        description: toolDef.function.description,
+        description: toolDef.function.description || undefined,
         parameters: toolDef.function.parameters
           ? normalizeJsonSchema(resolveJsonSchemaRefs(toolDef.function.parameters))
           : undefined,