feat: Add tool annotations for improved LLM tool understanding

Server/src/services/tools/batch_execute.py

@@ -4,6 +4,7 @@
 from typing import Annotated, Any
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
 
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
@@ -17,7 +18,14 @@
     name="batch_execute",
     description=(
         "Runs a list of MCP tool calls as one batch. Use it to send a full sequence of commands, "
-        "inspect the results, then submit the next batch for the following step."
+        "inspect the results, then submit the next batch for the following step. "
+        "Note: Safety characteristics depend on the tools contained in the batch—batches with only "
+        "read-only tools (e.g., find, get_info) are safe, while batches containing create/modify/delete "
+        "operations may be destructive."
+    ),
+    annotations=ToolAnnotations(
+        title="Batch Execute",
+        destructiveHint=True,
     ),
 )
 async def batch_execute(

Server/src/services/tools/debug_request_context.py

@@ -5,13 +5,19 @@
 from core.telemetry import get_package_version
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from transport.unity_instance_middleware import get_unity_instance_middleware
 from transport.plugin_hub import PluginHub
 
 
 @mcp_for_unity_tool(
-    description="Return the current FastMCP request context details (client_id, session_id, and meta dump)."
+    description="Return the current FastMCP request context details (client_id, session_id, and meta dump).",
+    annotations=ToolAnnotations(
+        title="Debug Request Context",
+        readOnlyHint=True,
+    ),
 )
 def debug_request_context(ctx: Context) -> dict[str, Any]:
     # Check request_context properties

Server/src/services/tools/execute_custom_tool.py

@@ -1,4 +1,5 @@
 from fastmcp import Context
+from mcp.types import ToolAnnotations
 from models.models import MCPResponse
 
 from services.custom_tool_service import (
@@ -12,6 +13,10 @@
 @mcp_for_unity_tool(
     name="execute_custom_tool",
     description="Execute a project-scoped custom tool registered by Unity.",
+    annotations=ToolAnnotations(
+        title="Execute Custom Tool",
+        destructiveHint=True,
+    ),
 )
 async def execute_custom_tool(ctx: Context, tool_name: str, parameters: dict | None = None) -> MCPResponse:
     unity_instance = get_unity_instance_from_context(ctx)

Server/src/services/tools/execute_menu_item.py

@@ -4,6 +4,7 @@
 from typing import Annotated, Any
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
 
 from models import MCPResponse
 from services.registry import mcp_for_unity_tool
@@ -13,7 +14,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Execute a Unity menu item by path."
+    description="Execute a Unity menu item by path.",
+    annotations=ToolAnnotations(
+        title="Execute Menu Item",
+        destructiveHint=True,
+    ),
 )
 async def execute_menu_item(
     ctx: Context,

Server/src/services/tools/find_in_file.py

@@ -5,6 +5,7 @@
 from urllib.parse import unquote, urlparse
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
 
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
@@ -64,7 +65,13 @@ def _split_uri(uri: str) -> tuple[str, str]:
     return name, directory
 
 
-@mcp_for_unity_tool(description="Searches a file with a regex pattern and returns line numbers and excerpts.")
+@mcp_for_unity_tool(
+    description="Searches a file with a regex pattern and returns line numbers and excerpts.",
+    annotations=ToolAnnotations(
+        title="Find in File",
+        readOnlyHint=True,
+    ),
+)
 async def find_in_file(
     ctx: Context,
     uri: Annotated[str, "The resource URI to search under Assets/ or file path form supported by read_resource"],

Server/src/services/tools/manage_asset.py

@@ -7,6 +7,8 @@
 from typing import Annotated, Any, Literal
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
 from services.tools.utils import parse_json_payload, coerce_int
@@ -20,7 +22,11 @@
         "Performs asset operations (import, create, modify, delete, etc.) in Unity.\n\n"
         "Tip (payload safety): for `action=\"search\"`, prefer paging (`page_size`, `page_number`) and keep "
         "`generate_preview=false` (previews can add large base64 blobs)."
-    )
+    ),
+    annotations=ToolAnnotations(
+        title="Manage Asset",
+        destructiveHint=True,
+    ),
 )
 async def manage_asset(
     ctx: Context,

Server/src/services/tools/manage_editor.py

@@ -1,6 +1,8 @@
 from typing import Annotated, Any, Literal
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from core.telemetry import is_telemetry_enabled, record_tool_usage
 from services.tools import get_unity_instance_from_context
@@ -10,7 +12,10 @@
 
 
 @mcp_for_unity_tool(
-    description="Controls and queries the Unity editor's state and settings. Tip: pass booleans as true/false; if your client only sends strings, 'true'/'false' are accepted."
+    description="Controls and queries the Unity editor's state and settings. Tip: pass booleans as true/false; if your client only sends strings, 'true'/'false' are accepted. Read-only actions: telemetry_status, telemetry_ping. Modifying actions: play, pause, stop, set_active_tool, add_tag, remove_tag, add_layer, remove_layer.",
+    annotations=ToolAnnotations(
+        title="Manage Editor",
+    ),
 )
 async def manage_editor(
     ctx: Context,

Server/src/services/tools/manage_gameobject.py

@@ -3,6 +3,8 @@
 from typing import Annotated, Any, Literal, Union
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
 from transport.unity_transport import send_with_unity_instance
@@ -12,7 +14,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Performs CRUD operations on GameObjects and components."
+    description="Performs CRUD operations on GameObjects and components. Read-only actions: find, get_components, get_component. Modifying actions: create, modify, delete, add_component, remove_component, set_component_property, duplicate, move_relative.",
+    annotations=ToolAnnotations(
+        title="Manage GameObject",
+        destructiveHint=True,
+    ),
 )
 async def manage_gameobject(
     ctx: Context,

Server/src/services/tools/manage_material.py

@@ -5,6 +5,8 @@
 from typing import Annotated, Any, Literal, Union
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
 from services.tools.utils import parse_json_payload
@@ -13,7 +15,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Manages Unity materials (set properties, colors, shaders, etc)."
+    description="Manages Unity materials (set properties, colors, shaders, etc). Read-only actions: ping, get_material_info. Modifying actions: create, set_material_shader_property, set_material_color, assign_material_to_renderer, set_renderer_color.",
+    annotations=ToolAnnotations(
+        title="Manage Material",
+        destructiveHint=True,
+    ),
 )
 async def manage_material(
     ctx: Context,

Server/src/services/tools/manage_prefabs.py

@@ -1,6 +1,8 @@
 from typing import Annotated, Any, Literal
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
 from transport.unity_transport import send_with_unity_instance
@@ -9,7 +11,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Performs prefab operations (open_stage, close_stage, save_open_stage, create_from_gameobject)."
+    description="Performs prefab operations (open_stage, close_stage, save_open_stage, create_from_gameobject).",
+    annotations=ToolAnnotations(
+        title="Manage Prefabs",
+        destructiveHint=True,
+    ),
 )
 async def manage_prefabs(
     ctx: Context,

Server/src/services/tools/manage_scene.py

@@ -1,6 +1,8 @@
 from typing import Annotated, Literal, Any
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
+
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
 from services.tools.utils import coerce_int, coerce_bool
@@ -10,7 +12,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Performs CRUD operations on Unity scenes."
+    description="Performs CRUD operations on Unity scenes. Read-only actions: get_hierarchy, get_active, get_build_settings, screenshot. Modifying actions: create, load, save.",
+    annotations=ToolAnnotations(
+        title="Manage Scene",
+        destructiveHint=True,
+    ),
 )
 async def manage_scene(
     ctx: Context,

Server/src/services/tools/manage_script.py

@@ -4,6 +4,7 @@
 from urllib.parse import urlparse, unquote
 
 from fastmcp import FastMCP, Context
+from mcp.types import ToolAnnotations
 
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
@@ -63,8 +64,9 @@ def _split_uri(uri: str) -> tuple[str, str]:
     return name, directory
 
 
-@mcp_for_unity_tool(description=(
-    """Apply small text edits to a C# script identified by URI.
+@mcp_for_unity_tool(
+    description=(
+        """Apply small text edits to a C# script identified by URI.
     IMPORTANT: This tool replaces EXACT character positions. Always verify content at target lines/columns BEFORE editing!
     RECOMMENDED WORKFLOW:
         1. First call resources/read with start_line/line_count to verify exact content
@@ -76,7 +78,12 @@ def _split_uri(uri: str) -> tuple[str, str]:
         - For pattern-based replacements, consider anchor operations in script_apply_edits
         - Lines, columns are 1-indexed
         - Tabs count as 1 column"""
-))
+    ),
+    annotations=ToolAnnotations(
+        title="Apply Text Edits",
+        destructiveHint=True,
+    ),
+)
 async def apply_text_edits(
     ctx: Context,
     uri: Annotated[str, "URI of the script to edit under Assets/ directory, unity://path/Assets/... or file://... or Assets/..."],
@@ -367,7 +374,13 @@ async def _flip_async():
     return {"success": False, "message": str(resp)}
 
 
-@mcp_for_unity_tool(description=("Create a new C# script at the given project path."))
+@mcp_for_unity_tool(
+    description="Create a new C# script at the given project path.",
+    annotations=ToolAnnotations(
+        title="Create Script",
+        destructiveHint=True,
+    ),
+)
 async def create_script(
     ctx: Context,
     path: Annotated[str, "Path under Assets/ to create the script at, e.g., 'Assets/Scripts/My.cs'"],
@@ -412,7 +425,13 @@ async def create_script(
     return resp if isinstance(resp, dict) else {"success": False, "message": str(resp)}
 
 
-@mcp_for_unity_tool(description=("Delete a C# script by URI or Assets-relative path."))
+@mcp_for_unity_tool(
+    description="Delete a C# script by URI or Assets-relative path.",
+    annotations=ToolAnnotations(
+        title="Delete Script",
+        destructiveHint=True,
+    ),
+)
 async def delete_script(
     ctx: Context,
     uri: Annotated[str, "URI of the script to delete under Assets/ directory, unity://path/Assets/... or file://... or Assets/..."],
@@ -434,7 +453,13 @@ async def delete_script(
     return resp if isinstance(resp, dict) else {"success": False, "message": str(resp)}
 
 
-@mcp_for_unity_tool(description=("Validate a C# script and return diagnostics."))
+@mcp_for_unity_tool(
+    description="Validate a C# script and return diagnostics.",
+    annotations=ToolAnnotations(
+        title="Validate Script",
+        readOnlyHint=True,
+    ),
+)
 async def validate_script(
     ctx: Context,
     uri: Annotated[str, "URI of the script to validate under Assets/ directory, unity://path/Assets/... or file://... or Assets/..."],
@@ -475,7 +500,13 @@ async def validate_script(
     return resp if isinstance(resp, dict) else {"success": False, "message": str(resp)}
 
 
-@mcp_for_unity_tool(description=("Compatibility router for legacy script operations. Prefer apply_text_edits (ranges) or script_apply_edits (structured) for edits."))
+@mcp_for_unity_tool(
+    description="Compatibility router for legacy script operations. Prefer apply_text_edits (ranges) or script_apply_edits (structured) for edits. Read-only action: read. Modifying actions: create, delete.",
+    annotations=ToolAnnotations(
+        title="Manage Script",
+        destructiveHint=True,
+    ),
+)
 async def manage_script(
     ctx: Context,
     action: Annotated[Literal['create', 'read', 'delete'], "Perform CRUD operations on C# scripts."],
@@ -543,14 +574,20 @@ async def manage_script(
         }
 
 
-@mcp_for_unity_tool(description=(
-    """Get manage_script capabilities (supported ops, limits, and guards).
+@mcp_for_unity_tool(
+    description=(
+        """Get manage_script capabilities (supported ops, limits, and guards).
     Returns:
         - ops: list of supported structured ops
         - text_ops: list of supported text ops
         - max_edit_payload_bytes: server edit payload cap
         - guards: header/using guard enabled flag"""
-))
+    ),
+    annotations=ToolAnnotations(
+        title="Manage Script Capabilities",
+        readOnlyHint=True,
+    ),
+)
 async def manage_script_capabilities(ctx: Context) -> dict[str, Any]:
     await ctx.info("Processing manage_script_capabilities")
     try:
@@ -575,7 +612,13 @@ async def manage_script_capabilities(ctx: Context) -> dict[str, Any]:
         return {"success": False, "error": f"capabilities error: {e}"}
 
 
-@mcp_for_unity_tool(description="Get SHA256 and basic metadata for a Unity C# script without returning file contents")
+@mcp_for_unity_tool(
+    description="Get SHA256 and basic metadata for a Unity C# script without returning file contents",
+    annotations=ToolAnnotations(
+        title="Get SHA",
+        readOnlyHint=True,
+    ),
+)
 async def get_sha(
     ctx: Context,
     uri: Annotated[str, "URI of the script to edit under Assets/ directory, unity://path/Assets/... or file://... or Assets/..."],

Server/src/services/tools/manage_scriptable_object.py

@@ -13,6 +13,7 @@
 from typing import Annotated, Any, Literal
 
 from fastmcp import Context
+from mcp.types import ToolAnnotations
 
 from services.registry import mcp_for_unity_tool
 from services.tools import get_unity_instance_from_context
@@ -22,7 +23,11 @@
 
 
 @mcp_for_unity_tool(
-    description="Creates and modifies ScriptableObject assets using Unity SerializedObject property paths."
+    description="Creates and modifies ScriptableObject assets using Unity SerializedObject property paths.",
+    annotations=ToolAnnotations(
+        title="Manage Scriptable Object",
+        destructiveHint=True,
+    ),
 )
 async def manage_scriptable_object(
     ctx: Context,