fix: sanitize empty Gemini object requirements

.changeset/gemini-mcp-schema-required.md

@@ -0,0 +1,5 @@
+---
+"@kilocode/cli": patch
+---
+
+Prevent Gemini requests from failing when MCP tool schemas contain `required` fields without matching object properties.

packages/opencode/src/provider/transform.ts

@@ -1487,9 +1487,15 @@ export function schema(model: Provider.Model, schema: JSONSchema7): JSONSchema7
       }
 
       // Filter required array to only include fields that exist in properties
-      if (result.type === "object" && result.properties && Array.isArray(result.required)) {
-        result.required = result.required.filter((field: any) => field in result.properties)
+      // kilocode_change start - Gemini rejects required entries without matching properties
+      if (result.type === "object" && Array.isArray(result.required)) {
+        const properties = isPlainObject(result.properties) ? result.properties : undefined
+        result.required = properties ? result.required.filter((field: any) => field in properties) : []
+        if (result.required.length === 0) {
+          delete result.required
+        }
       }
+      // kilocode_change end
 
       if (result.type === "array" && !hasCombiner(result)) {
         if (result.items == null) {

packages/opencode/test/provider/transform.test.ts

@@ -934,6 +934,53 @@ describe("ProviderTransform.schema - gemini non-object properties removal", () =
     expect(result.properties.data.required).toEqual(["name"])
   })
 
+  // kilocode_change start
+  test("removes required from object array items with no properties", () => {
+    const schema = {
+      type: "object",
+      properties: {
+        issue_fields: {
+          type: "array",
+          items: {
+            type: "object",
+            required: ["type"],
+          },
+        },
+      },
+    } as any
+
+    const result = ProviderTransform.schema(geminiModel, schema) as any
+
+    expect(result.properties.issue_fields.items.type).toBe("object")
+    expect(result.properties.issue_fields.items.required).toBeUndefined()
+  })
+
+  test("sanitizes gemini schemas routed through the Kilo Gateway", () => {
+    const gatewayGeminiModel = {
+      providerID: "kilocode",
+      api: {
+        id: "google/gemini-2.5-pro",
+      },
+    } as any
+    const schema = {
+      type: "object",
+      properties: {
+        issue_fields: {
+          type: "array",
+          items: {
+            type: "object",
+            required: ["type"],
+          },
+        },
+      },
+    } as any
+
+    const result = ProviderTransform.schema(gatewayGeminiModel, schema) as any
+
+    expect(result.properties.issue_fields.items.required).toBeUndefined()
+  })
+  // kilocode_change end
+
   test("does not affect non-gemini providers", () => {
     const openaiModel = {
       providerID: "openai",