diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt
index b199698aa7b..f98d5d3c403 100644
--- a/firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt
+++ b/firebase-ai/src/main/kotlin/com/google/firebase/ai/common/APIController.kt
@@ -67,6 +67,7 @@ import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withTimeout
 import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.json.ClassDiscriminatorMode
 import kotlinx.serialization.json.Json
 
 @OptIn(ExperimentalSerializationApi::class)
@@ -75,6 +76,7 @@ internal val JSON = Json {
   prettyPrint = false
   isLenient = true
   explicitNulls = false
+  classDiscriminatorMode = ClassDiscriminatorMode.NONE
 }
 
 /**
diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/FunctionDeclaration.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/FunctionDeclaration.kt
index 2b73d5ccfb1..65b753efda7 100644
--- a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/FunctionDeclaration.kt
+++ b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/FunctionDeclaration.kt
@@ -61,12 +61,12 @@ public class FunctionDeclaration(
   internal val schema: Schema =
     Schema.obj(properties = parameters, optionalProperties = optionalParameters, nullable = false)
 
-  internal fun toInternal() = Internal(name, description, schema.toInternal())
+  internal fun toInternal() = Internal(name, description, schema.toInternalOpenApi())
 
   @Serializable
   internal data class Internal(
     val name: String,
     val description: String,
-    val parameters: Schema.Internal
+    val parameters: Schema.InternalOpenAPI
   )
 }
diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerationConfig.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerationConfig.kt
index 7bab7fdf806..a496098787f 100644
--- a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerationConfig.kt
+++ b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerationConfig.kt
@@ -200,7 +200,7 @@ private constructor(
       frequencyPenalty = frequencyPenalty,
       presencePenalty = presencePenalty,
       responseMimeType = responseMimeType,
-      responseSchema = responseSchema?.toInternal(),
+      responseSchema = responseSchema?.toInternalOpenApi(),
       responseModalities = responseModalities?.map { it.toInternal() },
       thinkingConfig = thinkingConfig?.toInternal()
     )
@@ -216,7 +216,7 @@ private constructor(
     @SerialName("response_mime_type") val responseMimeType: String? = null,
     @SerialName("presence_penalty") val presencePenalty: Float? = null,
     @SerialName("frequency_penalty") val frequencyPenalty: Float? = null,
-    @SerialName("response_schema") val responseSchema: Schema.Internal? = null,
+    @SerialName("response_schema") val responseSchema: Schema.InternalOpenAPI? = null,
     @SerialName("response_modalities") val responseModalities: List<String>? = null,
     @SerialName("thinking_config") val thinkingConfig: ThinkingConfig.Internal? = null
   )
diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Part.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Part.kt
index 4312fd5bdbd..f11436aad56 100644
--- a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Part.kt
+++ b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Part.kt
@@ -23,7 +23,6 @@ import java.io.ByteArrayOutputStream
 import kotlinx.serialization.DeserializationStrategy
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
-import kotlinx.serialization.SerializationException
 import kotlinx.serialization.json.JsonContentPolymorphicSerializer
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonNull
diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Schema.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Schema.kt
index 5f2f6ca9350..1dfa4ddecb0 100644
--- a/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Schema.kt
+++ b/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Schema.kt
@@ -322,46 +322,147 @@ internal constructor(
     public fun anyOf(schemas: List<Schema>): Schema = Schema(type = "ANYOF", anyOf = schemas)
   }
 
-  internal fun toInternal(): Internal {
+  internal fun toInternalOpenApi(): InternalOpenAPI {
     val cleanedType =
       if (type == "ANYOF") {
         null
       } else {
         type
       }
-    return Internal(
+    return InternalOpenAPI(
       cleanedType,
       description,
       format,
       nullable,
       enum,
-      properties?.mapValues { it.value.toInternal() },
+      properties?.mapValues { it.value.toInternalOpenApi() },
       required,
-      items?.toInternal(),
+      items?.toInternalOpenApi(),
       title,
       minItems,
       maxItems,
       minimum,
       maximum,
-      anyOf?.map { it.toInternal() },
+      anyOf?.map { it.toInternalOpenApi() },
+    )
+  }
+
+  internal fun toInternalJson(): InternalJson {
+    val outType =
+      if (type == "ANYOF" || (type == "STRING" && format == "enum")) {
+        null
+      } else {
+        type.lowercase()
+      }
+
+    val (outMinimum, outMaximum) =
+      if (outType == "integer" && format == "int32") {
+        (minimum ?: Integer.MIN_VALUE.toDouble()) to (maximum ?: Integer.MAX_VALUE.toDouble())
+      } else {
+        minimum to maximum
+      }
+
+    val outFormat =
+      if (
+        (outType == "integer" && format == "int32") ||
+          (outType == "number" && format == "float") ||
+          format == "enum"
+      ) {
+        null
+      } else {
+        format
+      }
+
+    if (nullable == true) {
+      return InternalJsonNullable(
+        outType?.let { listOf(it, "null") },
+        description,
+        outFormat,
+        enum?.let {
+          buildList {
+            addAll(it)
+            add("null")
+          }
+        },
+        properties?.mapValues { it.value.toInternalJson() },
+        required,
+        items?.toInternalJson(),
+        title,
+        minItems,
+        maxItems,
+        outMinimum,
+        outMaximum,
+        anyOf?.map { it.toInternalJson() },
+      )
+    }
+    return InternalJsonNonNull(
+      outType,
+      description,
+      outFormat,
+      enum,
+      properties?.mapValues { it.value.toInternalJson() },
+      required,
+      items?.toInternalJson(),
+      title,
+      minItems,
+      maxItems,
+      outMinimum,
+      outMaximum,
+      anyOf?.map { it.toInternalJson() },
     )
   }
 
   @Serializable
-  internal data class Internal(
+  internal data class InternalOpenAPI(
     val type: String? = null,
     val description: String? = null,
     val format: String? = null,
     val nullable: Boolean? = false,
     val enum: List<String>? = null,
-    val properties: Map<String, Internal>? = null,
+    val properties: Map<String, InternalOpenAPI>? = null,
     val required: List<String>? = null,
-    val items: Internal? = null,
+    val items: InternalOpenAPI? = null,
     val title: String? = null,
     val minItems: Int? = null,
     val maxItems: Int? = null,
     val minimum: Double? = null,
     val maximum: Double? = null,
-    val anyOf: List<Internal>? = null,
+    val anyOf: List<InternalOpenAPI>? = null,
   )
+
+  @Serializable internal sealed interface InternalJson
+
+  @Serializable
+  internal data class InternalJsonNonNull(
+    val type: String? = null,
+    val description: String? = null,
+    val format: String? = null,
+    val enum: List<String>? = null,
+    val properties: Map<String, InternalJson>? = null,
+    val required: List<String>? = null,
+    val items: InternalJson? = null,
+    val title: String? = null,
+    val minItems: Int? = null,
+    val maxItems: Int? = null,
+    val minimum: Double? = null,
+    val maximum: Double? = null,
+    val anyOf: List<InternalJson>? = null,
+  ) : InternalJson
+
+  @Serializable
+  internal data class InternalJsonNullable(
+    val type: List<String>? = null,
+    val description: String? = null,
+    val format: String? = null,
+    val enum: List<String>? = null,
+    val properties: Map<String, InternalJson>? = null,
+    val required: List<String>? = null,
+    val items: InternalJson? = null,
+    val title: String? = null,
+    val minItems: Int? = null,
+    val maxItems: Int? = null,
+    val minimum: Double? = null,
+    val maximum: Double? = null,
+    val anyOf: List<InternalJson>? = null,
+  ) : InternalJson
 }
diff --git a/firebase-ai/src/test/java/com/google/firebase/ai/SchemaTests.kt b/firebase-ai/src/test/java/com/google/firebase/ai/SchemaTests.kt
index f9bdf8c835f..b275807d9b5 100644
--- a/firebase-ai/src/test/java/com/google/firebase/ai/SchemaTests.kt
+++ b/firebase-ai/src/test/java/com/google/firebase/ai/SchemaTests.kt
@@ -19,7 +19,9 @@ package com.google.firebase.ai
 import com.google.firebase.ai.type.Schema
 import com.google.firebase.ai.type.StringFormat
 import io.kotest.assertions.json.shouldEqualJson
+import java.io.File
 import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.ClassDiscriminatorMode
 import kotlinx.serialization.json.Json
 import org.junit.Test
 
@@ -93,7 +95,7 @@ internal class SchemaTests {
     """
         .trimIndent()
 
-    Json.encodeToString(schemaDeclaration.toInternal()).shouldEqualJson(expectedJson)
+    Json.encodeToString(schemaDeclaration.toInternalOpenApi()).shouldEqualJson(expectedJson)
   }
 
   @Test
@@ -216,6 +218,70 @@ internal class SchemaTests {
       """
         .trimIndent()
 
-    Json.encodeToString(schemaDeclaration.toInternal()).shouldEqualJson(expectedJson)
+    Json.encodeToString(schemaDeclaration.toInternalOpenApi()).shouldEqualJson(expectedJson)
   }
+
+  @Test
+  fun `schema encoding openAPI spec test`() {
+    val expectedSerialization = getSchemaJson("open-api-schema.json")
+    val serializedSchema = JSON_ENCODER.encodeToString(TEST_SCHEMA.toInternalOpenApi())
+    serializedSchema.shouldEqualJson(expectedSerialization)
+  }
+
+  @Test
+  fun `schema encoding jsonSchema spec test`() {
+    val expectedSerialization = getSchemaJson("json-schema.json")
+    val serializedSchema = JSON_ENCODER.encodeToString(TEST_SCHEMA.toInternalJson())
+    serializedSchema.shouldEqualJson(expectedSerialization)
+  }
+
+  internal fun getSchemaJson(filename: String): String {
+    return File("src/test/resources/vertexai-sdk-test-data/mock-responses/schema/${filename}")
+      .readText()
+  }
+
+  private val JSON_ENCODER = Json { classDiscriminatorMode = ClassDiscriminatorMode.NONE }
+
+  private val TEST_SCHEMA =
+    Schema.obj(
+      properties =
+        mapOf(
+          "integerTest" to Schema.integer(title = "integerTest", nullable = true),
+          "longTest" to
+            Schema.long(
+              title = "longTest",
+              nullable = false,
+              minimum = 0.0,
+              maximum = 5.0,
+              description = "a test long"
+            ),
+          "floatTest" to Schema.float(title = "floatTest", nullable = false),
+          "doubleTest" to Schema.double(title = "doubleTest", nullable = true),
+          "listTest" to
+            Schema.array(
+              items = Schema.integer(nullable = false),
+              title = "listTest",
+              nullable = false,
+              minItems = 0,
+              maxItems = 5
+            ),
+          "booleanTest" to Schema.boolean(title = "booleanTest", nullable = false),
+          "stringTest" to
+            Schema.string(title = "stringTest", format = StringFormat.Custom("email")),
+          "objTest" to
+            Schema.obj(
+              properties =
+                mapOf(
+                  "testInt" to Schema.integer(title = "testInt", nullable = false),
+                ),
+              title = "objTest",
+              description = "class kdoc should be used if property kdocs aren't present",
+              nullable = false
+            ),
+          "enumTest" to Schema.enumeration(values = listOf("val1", "val2", "val3"))
+        ),
+      optionalProperties = listOf("booleanTest"),
+      description = "A test kdoc",
+      nullable = false
+    )
 }
diff --git a/firebase-ai/src/test/java/com/google/firebase/ai/SerializationTests.kt b/firebase-ai/src/test/java/com/google/firebase/ai/SerializationTests.kt
index e6bea7a9e6f..476d68261d2 100644
--- a/firebase-ai/src/test/java/com/google/firebase/ai/SerializationTests.kt
+++ b/firebase-ai/src/test/java/com/google/firebase/ai/SerializationTests.kt
@@ -437,7 +437,7 @@ internal class SerializationTests {
     }
       """
         .trimIndent()
-    val actualJson = descriptorToJson(Schema.Internal.serializer().descriptor)
+    val actualJson = descriptorToJson(Schema.InternalOpenAPI.serializer().descriptor)
     expectedJsonAsString shouldEqualJson actualJson.toString()
   }
 
diff --git a/firebase-ai/update_responses.sh b/firebase-ai/update_responses.sh
index baf2676dfbb..881d63e2c53 100755
--- a/firebase-ai/update_responses.sh
+++ b/firebase-ai/update_responses.sh
@@ -17,7 +17,7 @@
 # This script replaces mock response files for Vertex AI unit tests with a fresh
 # clone of the shared repository of Vertex AI test data.
 
-RESPONSES_VERSION='v14.*' # The major version of mock responses to use
+RESPONSES_VERSION='v15.*' # The major version of mock responses to use
 REPO_NAME="vertexai-sdk-test-data"
 REPO_LINK="https://github.com/FirebaseExtended/$REPO_NAME.git"