fix: handle DeepResearch empty ResponseFunctionWebSearch.action after exceeding maxToolCalls (#600)

Ensure proper fallback and non-empty response handling when tool limit is exceeded.
This prevents returning empty responses during DeepResearch multi-call sequences.

Author: kuntal1461

openai-java-core/src/main/kotlin/com/openai/models/responses/ResponseFunctionWebSearch.kt

@@ -70,6 +70,15 @@ private constructor(
      */
     fun action(): Action = action.getRequired("action")
 
+    /**
+     * Returns the action if present.
+     *
+     * Unlike [action], this method returns an empty optional when the server omits the field,
+     * allowing callers to gracefully handle scenarios where the model did not provide tool
+     * parameters (for example, when `maxToolCalls` limits are reached).
+     */
+    fun actionOptional(): Optional<Action> = action.getOptional("action")
+
     /**
      * The status of the web search tool call.
      *
@@ -287,7 +296,7 @@ private constructor(
         }
 
         id()
-        action().validate()
+        action.getOptional("action").ifPresent { it.validate() }
         status().validate()
         _type().let {
             if (it != JsonValue.from("web_search_call")) {

openai-java-core/src/test/kotlin/com/openai/models/responses/ResponseFunctionWebSearchTest.kt

@@ -5,6 +5,7 @@ package com.openai.models.responses
 import com.fasterxml.jackson.module.kotlin.jacksonTypeRef
 import com.openai.core.jsonMapper
 import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatCode
 import org.junit.jupiter.api.Test
 
 internal class ResponseFunctionWebSearchTest {
@@ -72,4 +73,20 @@ internal class ResponseFunctionWebSearchTest {
 
         assertThat(roundtrippedResponseFunctionWebSearch).isEqualTo(responseFunctionWebSearch)
     }
+
+    @Test
+    fun deserializeWithoutAction() {
+        val jsonMapper = jsonMapper()
+        val payload = """
+            {"id":"ws_missing","status":"completed","type":"web_search_call"}
+        """.trimIndent()
+
+        val responseFunctionWebSearch =
+            jsonMapper.readValue(payload, jacksonTypeRef<ResponseFunctionWebSearch>())
+
+        assertThat(responseFunctionWebSearch.actionOptional()).isEmpty
+        assertThat(responseFunctionWebSearch.status())
+            .isEqualTo(ResponseFunctionWebSearch.Status.COMPLETED)
+        assertThatCode { responseFunctionWebSearch.validate() }.doesNotThrowAnyException()
+    }
 }