diff --git a/.changeset/fresh-mangos-fail.md b/.changeset/fresh-mangos-fail.md
new file mode 100644
index 0000000..ef79537
--- /dev/null
+++ b/.changeset/fresh-mangos-fail.md
@@ -0,0 +1,5 @@
+---
+"@inngest/agent-kit": patch
+---
+
+fix(adapters/openai): safely parse non-strong tool return value for Function calling
diff --git a/src/adapters/openai.ts b/src/adapters/openai.ts
index 4e9a975..97412c6 100644
--- a/src/adapters/openai.ts
+++ b/src/adapters/openai.ts
@@ -51,7 +51,11 @@ export const requestParser: AgenticModel.RequestParser<OpenAi.AiModel> = (
         case "tool_result":
           return {
             role: "tool",
-            content: m.content,
+            tool_call_id: m.tool.id,
+            content:
+              typeof m.content === "string"
+                ? m.content
+                : JSON.stringify(m.content),
           };
       }
     }) as AiAdapter.Input<OpenAi.AiModel>["messages"],