diff --git a/src/tools/tasks.ts b/src/tools/tasks.ts
index 99eb140..58731dc 100644
--- a/src/tools/tasks.ts
+++ b/src/tools/tasks.ts
@@ -5,7 +5,7 @@ import type { ToolContext } from './types.js';
 const ListTasksParams = Type.Object({
   project_slug: Type.Optional(Type.String({ description: 'Filter by project slug' })),
   status: Type.Optional(Type.String({ description: 'Filter by status: backlog|todo|in_progress|in_review|done' })),
-  assignee_slug: Type.Optional(Type.String({ description: 'Filter by assignee slug' })),
+  assignee_id: Type.Optional(Type.String({ description: 'Filter by assignee ID (UUID)' })),
 });
 
 const GetTaskParams = Type.Object({
@@ -26,7 +26,7 @@ const UpdateTaskParams = Type.Object({
   description: Type.Optional(Type.String({ description: 'New description' })),
   status: Type.Optional(Type.String({ description: 'New status: backlog|todo|in_progress|in_review|done' })),
   priority: Type.Optional(Type.String({ description: 'New priority: low|medium|high|critical' })),
-  assignee_slug: Type.Optional(Type.String({ description: 'Assignee slug (or null to unassign)' })),
+  assignee_id: Type.Optional(Type.String({ description: 'Assignee ID (UUID, or null to unassign)' })),
 });
 
 const TakeTaskParams = Type.Object({
@@ -51,13 +51,13 @@ export function createTaskTools(ctx: ToolContext): ToolDefinition<any>[] {
     {
       name: 'list_tasks',
       label: 'List Tasks',
-      description: 'List tasks with optional filters (project_slug, status, assignee_slug). Returns array of task objects.',
+      description: 'List tasks with optional filters (project_slug, status, assignee_id). Returns array of task objects.',
       parameters: ListTasksParams,
       async execute(_id: string, params: any) {
         const query: Record<string, string> = {};
         if (params.project_slug) query.project_slug = params.project_slug;
         if (params.status) query.status = params.status;
-        if (params.assignee_slug) query.assignee_slug = params.assignee_slug;
+        if (params.assignee_id) query.assignee_id = params.assignee_id;
         const tasks = await ctx.trackerClient.listTasks(query);
         return ok(JSON.stringify(tasks, null, 2));
       },
@@ -86,7 +86,7 @@ export function createTaskTools(ctx: ToolContext): ToolDefinition<any>[] {
     {
       name: 'update_task',
       label: 'Update Task',
-      description: 'Update task fields (title, description, status, priority, assignee_slug). Only pass fields you want to change.',
+      description: 'Update task fields (title, description, status, priority, assignee_id). Only pass fields you want to change.',
       parameters: UpdateTaskParams,
       async execute(_id: string, params: any) {
         const { task_id, ...fields } = params;