test(schema): add test for setting tool schemas with no argument input

internal/mcpserver/schema.go

@@ -221,12 +221,19 @@ func formatLogDuration(d time.Duration) string {
 	return fmt.Sprintf("%02d:%02d:%03d", minutes, seconds, milliseconds)
 }
 
+func normalizeObjectSchema(schema *jsonschema.Schema) {
+	if schema != nil && schema.Type == "object" && schema.Properties == nil {
+		schema.Properties = map[string]*jsonschema.Schema{}
+	}
+}
+
 func setToolSchemas[In any, Out any](tool *mcp.Tool) error {
 	if tool.InputSchema == nil {
 		inputSchema, err := jsonschema.For[In](toolSchemaOptions)
 		if err != nil {
 			return fmt.Errorf("infer input schema: %w", err)
 		}
+		normalizeObjectSchema(inputSchema)
 		tool.InputSchema = inputSchema
 	}
 

internal/mcpserver/schema_test.go

@@ -13,6 +13,24 @@ import (
 	"git.warky.dev/wdevs/amcs/internal/tools"
 )
 
+func TestSetToolSchemasAddsEmptyPropertiesForNoArgInput(t *testing.T) {
+	type noArgInput struct{}
+	type anyOutput struct{}
+
+	tool := &mcp.Tool{Name: "no_args"}
+	if err := setToolSchemas[noArgInput, anyOutput](tool); err != nil {
+		t.Fatalf("set tool schemas: %v", err)
+	}
+
+	schema, ok := tool.InputSchema.(*jsonschema.Schema)
+	if !ok {
+		t.Fatalf("input schema type = %T, want *jsonschema.Schema", tool.InputSchema)
+	}
+	if schema.Properties == nil {
+		t.Fatal("input schema missing properties: strict MCP clients require properties:{} on object schemas")
+	}
+}
+
 func TestSetToolSchemasUsesStringUUIDsInListOutput(t *testing.T) {
 	tool := &mcp.Tool{Name: "list_thoughts"}