diff --git a/common/src/main/kotlin/com/google/ai/client/generativeai/common/APIController.kt b/common/src/main/kotlin/com/google/ai/client/generativeai/common/APIController.kt
index faed8ee2..ebac13fd 100644
--- a/common/src/main/kotlin/com/google/ai/client/generativeai/common/APIController.kt
+++ b/common/src/main/kotlin/com/google/ai/client/generativeai/common/APIController.kt
@@ -240,7 +240,7 @@ private suspend fun validateResponse(response: HttpResponse) {
   if (message.contains("quota")) {
     throw QuotaExceededException(message)
   }
-  if (error.details.any { "SERVICE_DISABLED" == it.reason }) {
+  if (error.details?.any { "SERVICE_DISABLED" == it.reason } == true) {
     throw ServiceDisabledException(message)
   }
   throw ServerException(message)
diff --git a/common/src/main/kotlin/com/google/ai/client/generativeai/common/client/Types.kt b/common/src/main/kotlin/com/google/ai/client/generativeai/common/client/Types.kt
index cfc1e9d7..cb2fb478 100644
--- a/common/src/main/kotlin/com/google/ai/client/generativeai/common/client/Types.kt
+++ b/common/src/main/kotlin/com/google/ai/client/generativeai/common/client/Types.kt
@@ -30,6 +30,7 @@ data class GenerationConfig(
   @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? = null,
 )
 
 @Serializable data class Tool(val functionDeclarations: List<FunctionDeclaration>)
diff --git a/generativeai/src/commonMain/kotlin/dev/shreyaspatil/ai/client/generativeai/type/GenerationConfig.kt b/generativeai/src/commonMain/kotlin/dev/shreyaspatil/ai/client/generativeai/type/GenerationConfig.kt
index b9bb513a..bba0d3a1 100644
--- a/generativeai/src/commonMain/kotlin/dev/shreyaspatil/ai/client/generativeai/type/GenerationConfig.kt
+++ b/generativeai/src/commonMain/kotlin/dev/shreyaspatil/ai/client/generativeai/type/GenerationConfig.kt
@@ -39,6 +39,7 @@ private constructor(
   val maxOutputTokens: Int?,
   val stopSequences: List<String>?,
   val responseMimeType: String?,
+  val responseSchema: Schema<*>?,
 ) {
 
   class Builder {
@@ -49,6 +50,7 @@ private constructor(
     @JvmField var maxOutputTokens: Int? = null
     @JvmField var stopSequences: List<String>? = null
     @JvmField var responseMimeType: String? = null
+    @JvmField var responseSchema: Schema<*>? = null
 
     fun build() =
       GenerationConfig(
@@ -59,6 +61,7 @@ private constructor(
         maxOutputTokens = maxOutputTokens,
         stopSequences = stopSequences,
         responseMimeType = responseMimeType,
+        responseSchema = responseSchema,
       )
   }
 
diff --git a/generativeai/src/main/java/com/google/ai/client/generativeai/internal/util/conversions.kt b/generativeai/src/main/java/com/google/ai/client/generativeai/internal/util/conversions.kt
index 11eb1368..dadc2611 100644
--- a/generativeai/src/main/java/com/google/ai/client/generativeai/internal/util/conversions.kt
+++ b/generativeai/src/main/java/com/google/ai/client/generativeai/internal/util/conversions.kt
@@ -99,6 +99,7 @@ internal fun com.google.ai.client.generativeai.type.GenerationConfig.toInternal(
     maxOutputTokens = maxOutputTokens,
     stopSequences = stopSequences,
     responseMimeType = responseMimeType,
+    responseSchema = responseSchema?.toInternal(),
   )
 
 internal fun com.google.ai.client.generativeai.type.HarmCategory.toInternal() =
diff --git a/generativeai/src/main/java/com/google/ai/client/generativeai/type/FunctionDeclarations.kt b/generativeai/src/main/java/com/google/ai/client/generativeai/type/FunctionDeclarations.kt
new file mode 100644
index 00000000..80569ad7
--- /dev/null
+++ b/generativeai/src/main/java/com/google/ai/client/generativeai/type/FunctionDeclarations.kt
@@ -0,0 +1,271 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.ai.client.generativeai.type
+
+import org.json.JSONObject
+
+/**
+ * A declared function, including implementation, that a model can be given access to in order to
+ * gain info or complete tasks.
+ *
+ * @property name The name of the function call, this should be clear and descriptive for the model
+ * @property description A description of what the function does and its output.
+ * @property function the function implementation
+ */
+class NoParameterFunction(
+  name: String,
+  description: String,
+  val function: suspend () -> JSONObject,
+) : FunctionDeclaration(name, description) {
+  override fun getParameters() = listOf<Schema<Any>>()
+
+  suspend fun execute() = function()
+
+  override suspend fun execute(part: FunctionCallPart) = function()
+}
+
+/**
+ * A declared function, including implementation, that a model can be given access to in order to
+ * gain info or complete tasks.
+ *
+ * @property name The name of the function call, this should be clear and descriptive for the model
+ * @property description A description of what the function does and its output.
+ * @property param A description of the first function parameter
+ * @property function the function implementation
+ */
+class OneParameterFunction<T>(
+  name: String,
+  description: String,
+  val param: Schema<T>,
+  val function: suspend (T) -> JSONObject,
+) : FunctionDeclaration(name, description) {
+  override fun getParameters() = listOf(param)
+
+  override suspend fun execute(part: FunctionCallPart): JSONObject {
+    val arg1 = part.getArgOrThrow(param)
+    return function(arg1)
+  }
+}
+
+/**
+ * A declared function, including implementation, that a model can be given access to in order to
+ * gain info or complete tasks.
+ *
+ * @property name The name of the function call, this should be clear and descriptive for the model
+ * @property description A description of what the function does and its output.
+ * @property param1 A description of the first function parameter
+ * @property param2 A description of the second function parameter
+ * @property function the function implementation
+ */
+class TwoParameterFunction<T, U>(
+  name: String,
+  description: String,
+  val param1: Schema<T>,
+  val param2: Schema<U>,
+  val function: suspend (T, U) -> JSONObject,
+) : FunctionDeclaration(name, description) {
+  override fun getParameters() = listOf(param1, param2)
+
+  override suspend fun execute(part: FunctionCallPart): JSONObject {
+    val arg1 = part.getArgOrThrow(param1)
+    val arg2 = part.getArgOrThrow(param2)
+    return function(arg1, arg2)
+  }
+}
+
+/**
+ * A declared function, including implementation, that a model can be given access to in order to
+ * gain info or complete tasks.
+ *
+ * @property name The name of the function call, this should be clear and descriptive for the model
+ * @property description A description of what the function does and its output.
+ * @property param1 A description of the first function parameter
+ * @property param2 A description of the second function parameter
+ * @property param3 A description of the third function parameter
+ * @property function the function implementation
+ */
+class ThreeParameterFunction<T, U, V>(
+  name: String,
+  description: String,
+  val param1: Schema<T>,
+  val param2: Schema<U>,
+  val param3: Schema<V>,
+  val function: suspend (T, U, V) -> JSONObject,
+) : FunctionDeclaration(name, description) {
+  override fun getParameters() = listOf(param1, param2, param3)
+
+  override suspend fun execute(part: FunctionCallPart): JSONObject {
+    val arg1 = part.getArgOrThrow(param1)
+    val arg2 = part.getArgOrThrow(param2)
+    val arg3 = part.getArgOrThrow(param3)
+    return function(arg1, arg2, arg3)
+  }
+}
+
+/**
+ * A declared function, including implementation, that a model can be given access to in order to
+ * gain info or complete tasks.
+ *
+ * @property name The name of the function call, this should be clear and descriptive for the model
+ * @property description A description of what the function does and its output.
+ * @property param1 A description of the first function parameter
+ * @property param2 A description of the second function parameter
+ * @property param3 A description of the third function parameter
+ * @property param4 A description of the fourth function parameter
+ * @property function the function implementation
+ */
+class FourParameterFunction<T, U, V, W>(
+  name: String,
+  description: String,
+  val param1: Schema<T>,
+  val param2: Schema<U>,
+  val param3: Schema<V>,
+  val param4: Schema<W>,
+  val function: suspend (T, U, V, W) -> JSONObject,
+) : FunctionDeclaration(name, description) {
+  override fun getParameters() = listOf(param1, param2, param3, param4)
+
+  override suspend fun execute(part: FunctionCallPart): JSONObject {
+    val arg1 = part.getArgOrThrow(param1)
+    val arg2 = part.getArgOrThrow(param2)
+    val arg3 = part.getArgOrThrow(param3)
+    val arg4 = part.getArgOrThrow(param4)
+    return function(arg1, arg2, arg3, arg4)
+  }
+}
+
+abstract class FunctionDeclaration(val name: String, val description: String) {
+  abstract fun getParameters(): List<Schema<out Any?>>
+
+  abstract suspend fun execute(part: FunctionCallPart): JSONObject
+}
+
+/**
+ * Represents a parameter for a declared function
+ *
+ * @property name: The name of the parameter
+ * @property description: The description of what the parameter should contain or represent
+ * @property format: format information for the parameter, this can include bitlength in the case of
+ *   int/float or keywords like "enum" for the string type
+ * @property enum: contains the enum values for a string enum
+ * @property type: contains the type info and parser
+ * @property properties: if type is OBJECT, then this contains the description of the fields of the
+ *   object by name
+ * @property required: if type is OBJECT, then this contains the list of required keys
+ * @property items: if the type is ARRAY, then this contains a description of the objects in the
+ *   array
+ */
+class Schema<T>(
+  val name: String,
+  val description: String,
+  val format: String? = null,
+  val enum: List<String>? = null,
+  val properties: Map<String, Schema<out Any>>? = null,
+  val required: List<String>? = null,
+  val items: Schema<out Any>? = null,
+  val type: FunctionType<T>,
+) {
+  fun fromString(value: String?) = type.parse(value)
+
+  companion object {
+    /** Registers a schema for an integer number */
+    fun int(name: String, description: String) =
+      Schema<Long>(name = name, description = description, type = FunctionType.INTEGER)
+
+    /** Registers a schema for a string */
+    fun str(name: String, description: String) =
+      Schema<String>(name = name, description = description, type = FunctionType.STRING)
+
+    /** Registers a schema for a boolean */
+    fun bool(name: String, description: String) =
+      Schema<Boolean>(name = name, description = description, type = FunctionType.BOOLEAN)
+
+    /** Registers a schema for a floating point number */
+    fun num(name: String, description: String) =
+      Schema<Double>(name = name, description = description, type = FunctionType.NUMBER)
+
+    /**
+     * Registers a schema for a complex object. In a function it will be returned as a [JSONObject]
+     */
+    fun obj(name: String, description: String, vararg contents: Schema<out Any>) =
+      Schema<JSONObject>(
+        name = name,
+        description = description,
+        type = FunctionType.OBJECT,
+        required = contents.map { it.name },
+        properties = contents.associateBy { it.name }.toMap(),
+      )
+
+    /** Registers a schema for an array */
+    fun arr(name: String, description: String) =
+      Schema<List<String>>(name = name, description = description, type = FunctionType.ARRAY)
+
+    /** Registers a schema for an enum */
+    fun enum(name: String, description: String, values: List<String>) =
+      Schema<String>(
+        name = name,
+        description = description,
+        format = "enum",
+        enum = values,
+        type = FunctionType.STRING,
+      )
+  }
+}
+
+fun defineFunction(name: String, description: String, function: suspend () -> JSONObject) =
+  NoParameterFunction(name, description, function)
+
+fun <T> defineFunction(
+  name: String,
+  description: String,
+  arg1: Schema<T>,
+  function: suspend (T) -> JSONObject,
+) = OneParameterFunction(name, description, arg1, function)
+
+fun <T, U> defineFunction(
+  name: String,
+  description: String,
+  arg1: Schema<T>,
+  arg2: Schema<U>,
+  function: suspend (T, U) -> JSONObject,
+) = TwoParameterFunction(name, description, arg1, arg2, function)
+
+fun <T, U, W> defineFunction(
+  name: String,
+  description: String,
+  arg1: Schema<T>,
+  arg2: Schema<U>,
+  arg3: Schema<W>,
+  function: suspend (T, U, W) -> JSONObject,
+) = ThreeParameterFunction(name, description, arg1, arg2, arg3, function)
+
+fun <T, U, W, Z> defineFunction(
+  name: String,
+  description: String,
+  arg1: Schema<T>,
+  arg2: Schema<U>,
+  arg3: Schema<W>,
+  arg4: Schema<Z>,
+  function: suspend (T, U, W, Z) -> JSONObject,
+) = FourParameterFunction(name, description, arg1, arg2, arg3, arg4, function)
+
+private fun <T> FunctionCallPart.getArgOrThrow(param: Schema<T>): T {
+  return param.fromString(args[param.name])
+    ?: throw RuntimeException(
+      "Missing argument for parameter \"${param.name}\" for function \"$name\""
+    )
+}