feat(adk): tool reduction middleware

Author: N3kox

adk/middlewares/reduction/consts.go

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2026 CloudWeGo Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package reduction
+
+const (
+	lineTruncFmt    = `... (line truncated due to length limitation, %d chars total)`
+	contentTruncFmt = `... (content truncated due to length limitation, %d chars total)`
+)
+
+const (
+	toolOffloadResultFmt = `Tool result is too large, retrieve from %s if needed`
+)
+
+const (
+	msgReducedFlag   = "_reduction_mw_processed"
+	msgReducedTokens = "_reduction_mw_tokens"
+)