diff --git a/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/Assistant.kt b/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/Assistant.kt
index 6ada5a106..0c6ae72f4 100644
--- a/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/Assistant.kt
+++ b/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/Assistant.kt
@@ -11,8 +11,10 @@ import com.xebia.functional.openai.models.ext.assistant.AssistantToolsCode
 import com.xebia.functional.openai.models.ext.assistant.AssistantToolsFunction
 import com.xebia.functional.openai.models.ext.assistant.AssistantToolsRetrieval
 import com.xebia.functional.xef.llm.fromEnvironment
+import com.xebia.functional.xef.llm.models.functions.buildJsonSchema
 import io.ktor.util.logging.*
 import kotlinx.serialization.KSerializer
+import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonPrimitive
@@ -42,7 +44,7 @@ class Assistant(
       assistantsApi
     )
 
-  suspend inline fun getToolRegistered(name: String, args: String): JsonElement =
+  suspend inline fun getToolRegistered(name: String, args: String): ToolOutput =
     try {
       val toolConfig = toolsConfig.firstOrNull { it.functionObject.name == name }
 
@@ -51,20 +53,26 @@ class Assistant(
 
       val tool: Tool<Any?, Any?> = toolConfig.tool as Tool<Any?, Any?>
 
+      val schema = buildJsonSchema(toolSerializer.outputSerializer.descriptor)
       val output: Any? = tool(input)
-      ApiClient.JSON_DEFAULT.encodeToJsonElement(
-        toolSerializer.outputSerializer as KSerializer<Any?>,
-        output
-      )
+      val result =
+        ApiClient.JSON_DEFAULT.encodeToJsonElement(
+          toolSerializer.outputSerializer as KSerializer<Any?>,
+          output
+        )
+      ToolOutput(schema, result)
     } catch (e: Exception) {
       val message = "Error calling to tool registered $name: ${e.message}"
       val logger = KtorSimpleLogger("Functions")
       logger.error(message, e)
-      JsonObject(mapOf("error" to JsonPrimitive(message)))
+      val result = JsonObject(mapOf("error" to JsonPrimitive(message)))
+      ToolOutput(JsonObject(emptyMap()), result)
     }
 
   companion object {
 
+    @Serializable data class ToolOutput(val schema: JsonObject, val result: JsonElement)
+
     suspend operator fun invoke(
       model: String,
       name: String? = null,
diff --git a/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/AssistantThread.kt b/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/AssistantThread.kt
index 4cb07800c..3bb157905 100644
--- a/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/AssistantThread.kt
+++ b/core/src/commonMain/kotlin/com/xebia/functional/xef/llm/assistants/AssistantThread.kt
@@ -16,7 +16,6 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.FlowCollector
 import kotlinx.coroutines.flow.flow
 import kotlinx.serialization.encodeToString
-import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonObject
 
 class AssistantThread(
@@ -200,13 +199,12 @@ class AssistantThread(
         run.status == RunObject.Status.requires_action &&
           run.requiredAction?.type == RunObjectRequiredAction.Type.submit_tool_outputs
       ) {
-        val results: Map<String, JsonElement> =
+        val results: Map<String, Assistant.Companion.ToolOutput> =
           calls
             .filter { it.function != null }
             .parMap { toolCall ->
               val function = toolCall.function!!
-              val result: JsonElement =
-                assistant.getToolRegistered(function.name, function.arguments)
+              val result = assistant.getToolRegistered(function.name, function.arguments)
               toolCall.id to result
             }
             .toMap()
@@ -222,7 +220,11 @@ class AssistantThread(
                     results.map { (toolCallId, result) ->
                       SubmitToolOutputsRunRequestToolOutputsInner(
                         toolCallId = toolCallId,
-                        output = ApiClient.JSON_DEFAULT.encodeToString(result)
+                        output =
+                          ApiClient.JSON_DEFAULT.encodeToString(
+                            Assistant.Companion.ToolOutput.serializer(),
+                            result
+                          )
                       )
                     }
                 )