diff --git a/src/tools/event-crud-tools.ts b/src/tools/event-crud-tools.ts
index 1cdda63..76a75fd 100644
--- a/src/tools/event-crud-tools.ts
+++ b/src/tools/event-crud-tools.ts
@@ -26,6 +26,10 @@ export const CreateEventInputSchema = z.object({
   note: z.string().optional().describe('Event notes/description'),
   location: z.string().optional().describe('Event location'),
   url: z.string().optional().describe('Related URL'),
+  checklist: z.array(z.object({
+    checked: z.boolean().default(false).describe('Whether the checklist item is checked'),
+    title: z.string().min(1).describe('Checklist item title'),
+  })).optional().describe('Checklist items to attach to the event'),
 });
 
 export function createCreateEventTool(apiClient: TimeTreeAPIClient) {
@@ -35,7 +39,8 @@ export function createCreateEventTool(apiClient: TimeTreeAPIClient) {
       'Create a new event in a TimeTree calendar. Requires CSRF token (automatically managed). ' +
       'Returns the created event with UUID. ' +
       'Label colors (label_id 1-10): 1=Emerald green, 2=Modern cyan, 3=Deep sky blue, 4=Pastel brown, ' +
-      '5=Midnight black, 6=Apple red, 7=French rose, 8=Coral pink, 9=Bright orange, 10=Soft violet.',
+      '5=Midnight black, 6=Apple red, 7=French rose, 8=Coral pink, 9=Bright orange, 10=Soft violet. ' +
+      'Supports attaching checklist items.',
     inputSchema: {
       type: 'object',
       properties: {
@@ -94,6 +99,18 @@ export function createCreateEventTool(apiClient: TimeTreeAPIClient) {
           type: 'string',
           description: 'Related URL',
         },
+        checklist: {
+          type: 'array',
+          description: 'Checklist items to attach to the event',
+          items: {
+            type: 'object',
+            properties: {
+              checked: { type: 'boolean', description: 'Whether the item is checked' },
+              title: { type: 'string', description: 'Checklist item title' },
+            },
+            required: ['title'],
+          },
+        },
       },
       required: ['calendar_id', 'title', 'start_at', 'end_at'],
     },
@@ -117,6 +134,9 @@ export function createCreateEventTool(apiClient: TimeTreeAPIClient) {
           recurrences: [],
           alerts: [],
           file_uuids: [],
+          attachment: input.checklist
+            ? { checklist: input.checklist, virtual_user_attendees: [] }
+            : undefined,
         });
 
         // Format event for output
@@ -135,6 +155,7 @@ export function createCreateEventTool(apiClient: TimeTreeAPIClient) {
           note: event.note || null,
           url: event.url || null,
           category: event.category || null,
+          checklist: event.attachment?.checklist || null,
           created_at: event.created_at ? new Date(event.created_at).toISOString() : null,
           updated_at: event.updated_at ? new Date(event.updated_at).toISOString() : null,
         };
@@ -257,6 +278,10 @@ export const UpdateEventInputSchema = z.object({
   note: z.string().optional().describe('New event notes'),
   location: z.string().optional().describe('New event location'),
   url: z.string().optional().describe('New related URL'),
+  checklist: z.array(z.object({
+    checked: z.boolean().default(false).describe('Whether the checklist item is checked'),
+    title: z.string().min(1).describe('Checklist item title'),
+  })).optional().describe('Replace the event checklist items'),
 });
 
 export function createUpdateEventTool(apiClient: TimeTreeAPIClient) {
@@ -266,7 +291,8 @@ export function createUpdateEventTool(apiClient: TimeTreeAPIClient) {
       'Update an existing event in a TimeTree calendar. Only provide the fields you want to change. ' +
       'Requires CSRF token (automatically managed). Returns the updated event. ' +
       'Label colors (label_id 1-10): 1=Emerald green, 2=Modern cyan, 3=Deep sky blue, 4=Pastel brown, ' +
-      '5=Midnight black, 6=Apple red, 7=French rose, 8=Coral pink, 9=Bright orange, 10=Soft violet.',
+      '5=Midnight black, 6=Apple red, 7=French rose, 8=Coral pink, 9=Bright orange, 10=Soft violet. ' +
+      'Supports attaching checklist items.',
     inputSchema: {
       type: 'object',
       properties: {
@@ -326,6 +352,18 @@ export function createUpdateEventTool(apiClient: TimeTreeAPIClient) {
           type: 'string',
           description: 'New related URL',
         },
+        checklist: {
+          type: 'array',
+          description: 'Replace the event checklist items. Use [] to clear the checklist.',
+          items: {
+            type: 'object',
+            properties: {
+              checked: { type: 'boolean', description: 'Whether the item is checked' },
+              title: { type: 'string', description: 'Checklist item title' },
+            },
+            required: ['title'],
+          },
+        },
       },
       required: ['calendar_id', 'event_uuid'],
     },
@@ -352,6 +390,11 @@ export function createUpdateEventTool(apiClient: TimeTreeAPIClient) {
             note: input.note,
             location: input.location,
             url: input.url,
+            attachment: input.checklist === undefined
+              ? undefined
+              : input.checklist.length === 0
+                ? null
+                : { checklist: input.checklist },
           }
         );
 
@@ -371,6 +414,7 @@ export function createUpdateEventTool(apiClient: TimeTreeAPIClient) {
           note: event.note || null,
           url: event.url || null,
           category: event.category || null,
+          checklist: event.attachment?.checklist || null,
           updated_at: event.updated_at ? new Date(event.updated_at).toISOString() : null,
         };
 
diff --git a/src/tools/event-tools.ts b/src/tools/event-tools.ts
index 329053b..567e429 100644
--- a/src/tools/event-tools.ts
+++ b/src/tools/event-tools.ts
@@ -104,6 +104,7 @@ export function createGetEventsTool(apiClient: TimeTreeAPIClient) {
           updated_at: event.updated_at ? new Date(event.updated_at).toISOString() : null,
           has_alerts: event.alerts && event.alerts.length > 0,
           has_recurrence: event.recurrences && event.recurrences.length > 0,
+          checklist: event.attachment?.checklist || null,
         }));
 
         const result = {
@@ -256,6 +257,7 @@ export function createGetUpdatedEventsTool(apiClient: TimeTreeAPIClient) {
           updated_at: event.updated_at ? new Date(event.updated_at).toISOString() : null,
           has_alerts: event.alerts && event.alerts.length > 0,
           has_recurrence: event.recurrences && event.recurrences.length > 0,
+          checklist: event.attachment?.checklist || null,
         }));
 
         const result = {
diff --git a/src/types/timetree.ts b/src/types/timetree.ts
index 37856c9..2b95bbf 100644
--- a/src/types/timetree.ts
+++ b/src/types/timetree.ts
@@ -54,6 +54,12 @@ export const EventSchema = z.object({
   attendees: z.array(z.number()).optional(),
   recurrences: z.array(z.any()).optional(),
   alerts: z.array(z.any()).optional(),
+  attachment: z.object({
+    checklist: z.array(z.object({
+      checked: z.boolean().default(false),
+      title: z.string().min(1),
+    }).passthrough()).default([]),
+  }).passthrough().optional().nullable(),
   created_at: z.number().optional(),
   updated_at: z.number().optional(),
   // Allow additional fields but ignore them
@@ -110,7 +116,11 @@ export const CreateEventInputSchema = z.object({
   alerts: z.array(z.any()).default([]),
   file_uuids: z.array(z.string()).default([]),
   attachment: z.object({
-    url: z.string().url(),
+    url: z.string().url().optional(),
+    checklist: z.array(z.object({
+      checked: z.boolean().default(false),
+      title: z.string().min(1),
+    }).passthrough()).default([]),
     virtual_user_attendees: z.array(z.any()).default([]),
   }).optional(),
 }).passthrough();
@@ -138,9 +148,13 @@ export const UpdateEventInputSchema = z.object({
   alerts: z.array(z.any()).optional(),
   file_uuids: z.array(z.string()).optional(),
   attachment: z.object({
-    url: z.string().url(),
+    url: z.string().url().optional(),
+    checklist: z.array(z.object({
+      checked: z.boolean().default(false),
+      title: z.string().min(1),
+    }).passthrough()).optional(),
     virtual_user_attendees: z.array(z.any()).optional(),
-  }).optional(),
+  }).optional().nullable(),
 }).passthrough();
 
 export type UpdateEventInput = z.infer<typeof UpdateEventInputSchema>;
@@ -183,6 +197,10 @@ export const CreateEventToolInputSchema = z.object({
   note: z.string().optional(),
   location: z.string().optional(),
   url: z.string().optional(),
+  checklist: z.array(z.object({
+    checked: z.boolean().default(false),
+    title: z.string().min(1),
+  }).passthrough()).optional(),
 }).passthrough();
 
 export type CreateEventToolInput = z.infer<typeof CreateEventToolInputSchema>;
@@ -204,6 +222,10 @@ export const UpdateEventToolInputSchema = z.object({
   note: z.string().optional(),
   location: z.string().optional(),
   url: z.string().optional(),
+  checklist: z.array(z.object({
+    checked: z.boolean().default(false),
+    title: z.string().min(1),
+  }).passthrough()).optional(),
 }).passthrough();
 
 export type UpdateEventToolInput = z.infer<typeof UpdateEventToolInputSchema>;