1 files changed, 21 insertions, 1 deletions
diff --git a/libpanto/src/anthropic_messages_json.zig b/libpanto/src/anthropic_messages_json.zig
index f8bfc2e..d382de8 100644
--- a/libpanto/src/anthropic_messages_json.zig
+++ b/libpanto/src/anthropic_messages_json.zig
@@ -111,6 +111,26 @@ fn writeRawJson(s: *std.json.Stringify, raw: []const u8) !void {
     try s.write(parsed.value);
 }
 
+fn writeToolUseInput(s: *std.json.Stringify, raw: []const u8) !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const parsed = std.json.parseFromSlice(std.json.Value, arena.allocator(), raw, .{}) catch {
+        try s.beginObject();
+        try s.objectField("_invalid_input");
+        try s.write(raw);
+        try s.endObject();
+        return;
+    };
+    if (parsed.value != .object) {
+        try s.beginObject();
+        try s.objectField("_invalid_input");
+        try s.write(raw);
+        try s.endObject();
+        return;
+    }
+    try s.write(parsed.value);
+}
+
 /// Build the top-level Anthropic `system` string. Applies the shared
 /// append/replace derivation (see `conversation.effectiveSystemBlocks`),
 /// strips trailing newlines from each surviving block, and joins them with
@@ -200,7 +220,7 @@ fn writeBlock(s: *std.json.Stringify, block: conversation.ContentBlock) !void {
                 try s.beginObject();
                 try s.endObject();
             } else {
-                try writeRawJson(s, input_bytes);
+                try writeToolUseInput(s, input_bytes);
             }
             try s.endObject();
         },