diff --git a/apps/api/src/api/tool_instances.py b/apps/api/src/api/tool_instances.py
index e17d42f..1d5f9ba 100644
--- a/apps/api/src/api/tool_instances.py
+++ b/apps/api/src/api/tool_instances.py
@@ -5,6 +5,7 @@ import uuid
 from datetime import datetime
 
 from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel, Field
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -29,6 +30,13 @@ from src.services.docker import (
 router = APIRouter(prefix="/projects", tags=["tool-instances"])
 
 
+class CreateInstanceRequest(BaseModel):
+    """Request body for creating a tool instance."""
+
+    tool_type_id: str = Field(description="UUID of the tool type to instantiate")
+    display_name: str | None = Field(default=None, description="Optional display name for the instance")
+
+
 async def _get_user(session: AsyncSession, user_id: uuid.UUID) -> User:
     """Fetch a user by ID or raise 404 if not found."""
     user = await session.get(User, user_id)
@@ -71,8 +79,7 @@ async def _get_owned_project(
 async def create_instance(
     project_id: uuid.UUID,
     repo_id: uuid.UUID,
-    tool_type_id: uuid.UUID,
-    display_name: str | None = None,
+    data: CreateInstanceRequest,
     user_id: uuid.UUID = Depends(get_current_user_id),
     session: AsyncSession = Depends(get_db_session),
 ) -> dict:
@@ -98,6 +105,7 @@ async def create_instance(
             status_code=status.HTTP_404_NOT_FOUND, detail="repository not found"
         )
 
+    tool_type_id = uuid.UUID(data.tool_type_id)
     tool_type = await session.get(ToolType, tool_type_id)
     if tool_type is None:
         raise HTTPException(
@@ -106,7 +114,7 @@ async def create_instance(
 
     # Generate unique name
     instance_name = f"{tool_type.name}-{repo.name}-{uuid.uuid4().hex[:8]}"
-    instance_display = display_name or f"{tool_type.display_name} - {repo.name}"
+    instance_display = data.display_name or f"{tool_type.display_name} - {repo.name}"
 
     # Create instance directory
     instance_dir = ensure_instance_directory(instance_name)