fix: provide fallback items for Gemini array params

astrbot/core/agent/tool.py

@@ -293,7 +293,17 @@ def convert_schema(schema: dict) -> dict:
                 if properties:
                     result["properties"] = properties
 
-            if "items" in schema:
+            if target_type == "array":
+                # Gemini rejects array schemas that omit `items`, while JSON Schema
+                # producers in the wild (especially external MCP tools) sometimes
+                # leave element types unspecified. Fall back to a permissive string
+                # item schema so tool calling stays functional instead of failing the
+                # whole request with `items: missing field`.
+                if isinstance(schema.get("items"), dict) and schema["items"]:
+                    result["items"] = convert_schema(schema["items"])
+                else:
+                    result["items"] = {"type": "string"}
+            elif "items" in schema:
                 result["items"] = convert_schema(schema["items"])
 
             return result

tests/unit/test_tool_google_schema.py

@@ -0,0 +1,47 @@
+from astrbot.core.agent.tool import FunctionTool, ToolSet
+
+
+def test_google_schema_adds_default_items_for_array_parameters_without_items():
+    tool = FunctionTool(
+        name="lookup_sources",
+        description="Look up sources by UUID.",
+        parameters={
+            "type": "object",
+            "properties": {
+                "source_uuids": {
+                    "type": "array",
+                    "description": "Source UUIDs to fetch.",
+                }
+            },
+        },
+    )
+
+    schema = ToolSet(tools=[tool]).google_schema()
+    source_uuids = schema["function_declarations"][0]["parameters"]["properties"][
+        "source_uuids"
+    ]
+
+    assert source_uuids["type"] == "array"
+    assert source_uuids["items"] == {"type": "string"}
+
+
+def test_google_schema_preserves_explicit_array_item_schema():
+    tool = FunctionTool(
+        name="lookup_numbers",
+        description="Look up integer values.",
+        parameters={
+            "type": "object",
+            "properties": {
+                "numbers": {
+                    "type": "array",
+                    "items": {"type": "integer", "format": "int32"},
+                }
+            },
+        },
+    )
+
+    schema = ToolSet(tools=[tool]).google_schema()
+    numbers = schema["function_declarations"][0]["parameters"]["properties"]["numbers"]
+
+    assert numbers["type"] == "array"
+    assert numbers["items"] == {"type": "integer", "format": "int32"}