From a792106f2bd1b1dff3691b3c2ea58997482445ab Mon Sep 17 00:00:00 2001
From: hanzheng1954 <62579748+hanzheng1954@users.noreply.github.com>
Date: Mon, 29 Jun 2026 22:33:24 +0800
Subject: [PATCH] fix: ensure input_schema is always present for Vertex AI
 proxy compatibility

Some proxies (e.g. Vertex AI via Langdock) strictly require input_schema
to be present on every tool object, even server-side tools where
Anthropic's own API accepts omitting it.

When InputSchema is nil (e.g. for web_search_20250305 server-side tool),
the omitempty JSON tag causes the key to be absent entirely, triggering
a 400 error from strict proxies:

  {"message":[{"expected":"object","code":"invalid_type",
   "path":["tools",9,"input_schema"],
   "message":"Invalid input: expected object, received undefined"}]}

Fix: default to empty object schema {"type":"object","properties":{}} when
InputSchema is nil in fromLLMTool.
---
 llm/ant/ant.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/llm/ant/ant.go b/llm/ant/ant.go
index 6eaa3ee4..785a7f3c 100644
--- a/llm/ant/ant.go
+++ b/llm/ant/ant.go
@@ -608,11 +608,18 @@ func fromLLMToolChoice(tc *llm.ToolChoice) *toolChoice {
 }
 
 func fromLLMTool(t *llm.Tool) *tool {
+	schema := t.InputSchema
+	if schema == nil {
+		// Some proxies (e.g. Vertex AI via Langdock) strictly require input_schema
+		// to be present on every tool, even server-side tools where Anthropic's
+		// own API accepts omitting it. Default to an empty object schema.
+		schema = json.RawMessage(`{"type":"object","properties":{}}`)
+	}
 	return &tool{
 		Name:         t.Name,
 		Type:         t.Type,
 		Description:  t.Description,
-		InputSchema:  t.InputSchema,
+		InputSchema:  schema,
 		CacheControl: fromLLMCache(t.Cache),
 	}
 }