diff --git a/astrbot/core/agent/tool.py b/astrbot/core/agent/tool.py
index 2cf6b6747c0..9e31fcc60db 100644
--- a/astrbot/core/agent/tool.py
+++ b/astrbot/core/agent/tool.py
@@ -1,4 +1,5 @@
 import copy
+import json
 from collections.abc import AsyncGenerator, Awaitable, Callable
 from typing import Any, Generic
 
@@ -303,6 +304,25 @@ def convert_schema(schema: dict) -> dict:
             }
             result.update({k: schema[k] for k in support_fields if k in schema})
 
+            # Gemini only accepts string enums ("enum: only allowed for STRING
+            # type"). Other fields keep their type, so the model still sends
+            # e.g. an integer, and list the allowed values in the description.
+            if "enum" in result:
+                enum = result.pop("enum")
+                values = [v for v in enum if v is not None]
+                if None in enum:
+                    result["nullable"] = True
+                if result["type"] == "string":
+                    result["enum"] = [
+                        v if isinstance(v, str) else json.dumps(v) for v in values
+                    ]
+                else:
+                    allowed = ", ".join(json.dumps(v) for v in values)
+                    description = result.get("description", "")
+                    result["description"] = (
+                        f"{description}\nAllowed values: {allowed}".strip()
+                    )
+
             if "properties" in schema:
                 properties = {}
                 for key, value in schema["properties"].items():
diff --git a/tests/unit/test_tool_google_schema.py b/tests/unit/test_tool_google_schema.py
index 0826e99e77d..6385778ec5a 100644
--- a/tests/unit/test_tool_google_schema.py
+++ b/tests/unit/test_tool_google_schema.py
@@ -6,6 +6,8 @@
 from pathlib import Path
 from typing import Generic, TypeVar
 
+from google.genai import types as genai_types
+
 REPO_ROOT = Path(__file__).resolve().parents[2]
 TOOL_MODULE_PATH = REPO_ROOT / "astrbot/core/agent/tool.py"
 
@@ -77,6 +79,49 @@ def test_google_schema_fills_missing_array_items_with_string_schema():
     assert source_uuids["items"] == {"type": "string"}
 
 
+def test_google_schema_keeps_enums_only_on_string_fields():
+    tool_module = load_tool_module()
+    FunctionTool = tool_module.FunctionTool
+    ToolSet = tool_module.ToolSet
+
+    tool = FunctionTool(
+        name="list_items",
+        description="List items.",
+        parameters={
+            "type": "object",
+            "properties": {
+                "page_size": {
+                    "type": "integer",
+                    "description": "Items per page.",
+                    "enum": [10, 20, 50],
+                },
+                "strict": {"type": "boolean", "enum": [True]},
+                "order": {"type": ["string", "null"], "enum": ["asc", "desc", None]},
+            },
+        },
+    )
+
+    schema = ToolSet([tool]).google_schema()
+    properties = schema["function_declarations"][0]["parameters"]["properties"]
+
+    assert properties["page_size"] == {
+        "type": "integer",
+        "description": "Items per page.\nAllowed values: 10, 20, 50",
+    }
+    assert properties["strict"] == {
+        "type": "boolean",
+        "description": "Allowed values: true",
+    }
+    assert properties["order"] == {
+        "type": "string",
+        "enum": ["asc", "desc"],
+        "nullable": True,
+    }
+    assert tool.parameters["properties"]["page_size"]["enum"] == [10, 20, 50]
+    # The Gemini SDK rejects non-string enum values when the request is built.
+    genai_types.Tool(function_declarations=schema["function_declarations"])
+
+
 def test_openai_schema_sorts_tools_by_name_without_mutating_toolset_order():
     tool_module = load_tool_module()
     FunctionTool = tool_module.FunctionTool