Function calling support for on device sdk.

ai-logic/firebase-ai-ondevice-interop/CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- [feature] Added support for function calling in on-device content generation
+  requests and responses. (#8758)
 - [changed] **Breaking Change**: Updated `GenerateContentRequest` to accept a
   `List<Part>` instead of a single `TextPart` and optional `ImagePart`. (#8754)
 

ai-logic/firebase-ai-ondevice-interop/api.txt

@@ -3,9 +3,12 @@ package com.google.firebase.ai.ondevice.interop {
 
   public final class Candidate {
     ctor public Candidate(String text, com.google.firebase.ai.ondevice.interop.FinishReason finishReason);
+    ctor public Candidate(String text, com.google.firebase.ai.ondevice.interop.FinishReason finishReason, java.util.List<com.google.firebase.ai.ondevice.interop.FunctionCallPart> functionCalls = emptyList());
     method public com.google.firebase.ai.ondevice.interop.FinishReason getFinishReason();
+    method public java.util.List<com.google.firebase.ai.ondevice.interop.FunctionCallPart> getFunctionCalls();
     method public String getText();
     property public final com.google.firebase.ai.ondevice.interop.FinishReason finishReason;
+    property public final java.util.List<com.google.firebase.ai.ondevice.interop.FunctionCallPart> functionCalls;
     property public final String text;
   }
 
@@ -78,15 +81,81 @@ package com.google.firebase.ai.ondevice.interop {
     ctor public FirebaseAIOnDeviceUnknownException(String message, Throwable? cause = null);
   }
 
+  public final class FunctionCallPart implements com.google.firebase.ai.ondevice.interop.Part {
+    ctor public FunctionCallPart(String name, java.util.Map<java.lang.String,? extends java.lang.Object?> args);
+    ctor public FunctionCallPart(String name, java.util.Map<java.lang.String,? extends java.lang.Object?> args, String? id = null);
+    method public java.util.Map<java.lang.String,java.lang.Object?> getArgs();
+    method public String? getId();
+    method public String getName();
+    property public final java.util.Map<java.lang.String,java.lang.Object?> args;
+    property public final String? id;
+    property public final String name;
+  }
+
+  public final class FunctionDeclaration {
+    ctor public FunctionDeclaration(String name, String description);
+    ctor public FunctionDeclaration(String name, String description, com.google.firebase.ai.ondevice.interop.FunctionSchema? parameters = null);
+    method public String getDescription();
+    method public String getName();
+    method public com.google.firebase.ai.ondevice.interop.FunctionSchema? getParameters();
+    property public final String description;
+    property public final String name;
+    property public final com.google.firebase.ai.ondevice.interop.FunctionSchema? parameters;
+  }
+
+  public final class FunctionResponsePart implements com.google.firebase.ai.ondevice.interop.Part {
+    ctor public FunctionResponsePart(String name, java.util.Map<java.lang.String,? extends java.lang.Object?> response);
+    ctor public FunctionResponsePart(String name, java.util.Map<java.lang.String,? extends java.lang.Object?> response, String? id = null);
+    method public String? getId();
+    method public String getName();
+    method public java.util.Map<java.lang.String,java.lang.Object?> getResponse();
+    property public final String? id;
+    property public final String name;
+    property public final java.util.Map<java.lang.String,java.lang.Object?> response;
+  }
+
+  public final class FunctionSchema {
+    ctor public FunctionSchema(String type);
+    ctor public FunctionSchema(String type, String? description = null);
+    ctor public FunctionSchema(String type, String? description = null, java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties = emptyMap());
+    ctor public FunctionSchema(String type, String? description = null, java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties = emptyMap(), java.util.List<java.lang.String> required = emptyList());
+    ctor public FunctionSchema(String type, String? description = null, java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties = emptyMap(), java.util.List<java.lang.String> required = emptyList(), java.util.List<java.lang.String>? enum = null);
+    ctor public FunctionSchema(String type, String? description = null, java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties = emptyMap(), java.util.List<java.lang.String> required = emptyList(), java.util.List<java.lang.String>? enum = null, Boolean? nullable = null);
+    ctor public FunctionSchema(String type, String? description = null, java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties = emptyMap(), java.util.List<java.lang.String> required = emptyList(), java.util.List<java.lang.String>? enum = null, Boolean? nullable = null, com.google.firebase.ai.ondevice.interop.FunctionSchema? items = null);
+    method public String? getDescription();
+    method public java.util.List<java.lang.String>? getEnum();
+    method public com.google.firebase.ai.ondevice.interop.FunctionSchema? getItems();
+    method public Boolean? getNullable();
+    method public java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> getProperties();
+    method public java.util.List<java.lang.String> getRequired();
+    method public String getType();
+    property public final String? description;
+    property public final java.util.List<java.lang.String>? enum;
+    property public final com.google.firebase.ai.ondevice.interop.FunctionSchema? items;
+    property public final Boolean? nullable;
+    property public final java.util.Map<java.lang.String,com.google.firebase.ai.ondevice.interop.FunctionSchema> properties;
+    property public final java.util.List<java.lang.String> required;
+    property public final String type;
+  }
+
   public final class GenerateContentRequest {
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null, Integer? candidateCount = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null, Integer? candidateCount = null, Integer? maxOutputTokens = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null, Integer? candidateCount = null, Integer? maxOutputTokens = null, com.google.firebase.ai.ondevice.interop.TextPart? systemInstruction = null);
     ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null, Integer? candidateCount = null, Integer? maxOutputTokens = null, com.google.firebase.ai.ondevice.interop.TextPart? systemInstruction = null, Boolean? enableThinking = null);
+    ctor public GenerateContentRequest(java.util.List<? extends com.google.firebase.ai.ondevice.interop.Part> parts, Float? temperature = null, Integer? topK = null, Integer? seed = null, Integer? candidateCount = null, Integer? maxOutputTokens = null, com.google.firebase.ai.ondevice.interop.TextPart? systemInstruction = null, Boolean? enableThinking = null, java.util.List<com.google.firebase.ai.ondevice.interop.FunctionDeclaration> tools = emptyList());
     method public Integer? getCandidateCount();
     method public Boolean? getEnableThinking();
     method public Integer? getMaxOutputTokens();
     method public java.util.List<com.google.firebase.ai.ondevice.interop.Part> getParts();
     method public Integer? getSeed();
     method public com.google.firebase.ai.ondevice.interop.TextPart? getSystemInstruction();
     method public Float? getTemperature();
+    method public java.util.List<com.google.firebase.ai.ondevice.interop.FunctionDeclaration> getTools();
     method public Integer? getTopK();
     property public final Integer? candidateCount;
     property public final Boolean? enableThinking;
@@ -95,6 +164,7 @@ package com.google.firebase.ai.ondevice.interop {
     property public final Integer? seed;
     property public final com.google.firebase.ai.ondevice.interop.TextPart? systemInstruction;
     property public final Float? temperature;
+    property public final java.util.List<com.google.firebase.ai.ondevice.interop.FunctionDeclaration> tools;
     property public final Integer? topK;
   }
 
@@ -133,6 +203,7 @@ package com.google.firebase.ai.ondevice.interop {
     method public suspend Object? getBaseModelName(kotlin.coroutines.Continuation<? super java.lang.String>);
     method public suspend Object? getTokenLimit(kotlin.coroutines.Continuation<? super java.lang.Integer>);
     method public suspend Object? isAvailable(kotlin.coroutines.Continuation<? super java.lang.Boolean>);
+    method public suspend Object? isFunctionCallingAvailable(kotlin.coroutines.Continuation<? super java.lang.Boolean>);
     method public suspend Object? isThinkingModeAvailable(kotlin.coroutines.Continuation<? super java.lang.Boolean>);
     method public suspend Object? warmup(kotlin.coroutines.Continuation<? super kotlin.Unit>);
   }

ai-logic/firebase-ai-ondevice-interop/src/main/kotlin/com/google/firebase/ai/ondevice/interop/Candidate.kt

@@ -26,4 +26,10 @@ public class FinishReason private constructor(public val name: String) {
 }
 
 /** A `Candidate` represents a single response generated by the model for a given request. */
-public class Candidate(public val text: String, public val finishReason: FinishReason) {}
+public class Candidate
+@JvmOverloads
+constructor(
+  public val text: String,
+  public val finishReason: FinishReason,
+  public val functionCalls: List<FunctionCallPart> = emptyList()
+)

ai-logic/firebase-ai-ondevice-interop/src/main/kotlin/com/google/firebase/ai/ondevice/interop/FunctionDeclaration.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2026 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.firebase.ai.ondevice.interop
+
+/**
+ * Defines a function that the model can use as a tool for on-device inference.
+ *
+ * @property name The name of the function.
+ * @property description The description of what the function does.
+ * @property parameters The schema describing the parameters the function accepts.
+ */
+public class FunctionDeclaration
+@JvmOverloads
+constructor(
+  public val name: String,
+  public val description: String,
+  public val parameters: FunctionSchema? = null
+)
+
+/**
+ * Schema defining the structure of function parameters for on-device function calling.
+ *
+ * @property type The data type of the schema (for example, OBJECT, STRING, INTEGER, BOOLEAN,
+ * ARRAY).
+ * @property description An optional description of what the value represents.
+ * @property properties The map of property names to schemas when type is OBJECT.
+ * @property required The list of required property names when type is OBJECT.
+ * @property enum The list of allowed string values when applicable.
+ * @property nullable Indicates whether the value can be null.
+ * @property items The schema for array elements when type is ARRAY.
+ */
+public class FunctionSchema
+@JvmOverloads
+constructor(
+  public val type: String,
+  public val description: String? = null,
+  public val properties: Map<String, FunctionSchema> = emptyMap(),
+  public val required: List<String> = emptyList(),
+  public val enum: List<String>? = null,
+  public val nullable: Boolean? = null,
+  public val items: FunctionSchema? = null
+)

ai-logic/firebase-ai-ondevice-interop/src/main/kotlin/com/google/firebase/ai/ondevice/interop/GenerateContentRequest.kt

@@ -31,8 +31,11 @@ package com.google.firebase.ai.ondevice.interop
  * response.
  * @property systemInstruction Instructions that direct the model to behave a certain way.
  * @property enableThinking Whether to enable thinking mode for the model.
+ * @property tools The list of function declaration tools available to the model.
  */
-public class GenerateContentRequest(
+public class GenerateContentRequest
+@JvmOverloads
+constructor(
   public val parts: List<Part>,
   public val temperature: Float? = null,
   public val topK: Int? = null,
@@ -41,4 +44,5 @@ public class GenerateContentRequest(
   public val maxOutputTokens: Int? = null,
   public val systemInstruction: TextPart? = null,
   public val enableThinking: Boolean? = null,
+  public val tools: List<FunctionDeclaration> = emptyList(),
 ) {}

ai-logic/firebase-ai-ondevice-interop/src/main/kotlin/com/google/firebase/ai/ondevice/interop/GenerativeModel.kt

@@ -43,6 +43,13 @@ public interface GenerativeModel {
    */
   public suspend fun isThinkingModeAvailable(): Boolean
 
+  /**
+   * Checks whether function calling is available on the model.
+   *
+   * @return `true` if function calling is available, `false` otherwise.
+   */
+  public suspend fun isFunctionCallingAvailable(): Boolean
+
   /**
    * Generates new content from the input [GenerateContentRequest] given to the model as a prompt.
    *

ai-logic/firebase-ai-ondevice-interop/src/main/kotlin/com/google/firebase/ai/ondevice/interop/Part.kt

@@ -26,3 +26,50 @@ public class TextPart(public val text: String) : Part
 
 /** Represents image data. */
 public class ImagePart(public val bitmap: Bitmap) : Part
+
+/**
+ * Represents function call name and parameters emitted by the model or sent in conversation
+ * history.
+ */
+public class FunctionCallPart
+@JvmOverloads
+constructor(
+  public val name: String,
+  public val args: Map<String, Any?>,
+  public val id: String? = null
+) : Part {
+  override fun equals(other: Any?): Boolean {
+    if (this === other) return true
+    if (other !is FunctionCallPart) return false
+    return name == other.name && args == other.args && id == other.id
+  }
+
+  override fun hashCode(): Int {
+    var result = name.hashCode()
+    result = 31 * result + args.hashCode()
+    result = 31 * result + (id?.hashCode() ?: 0)
+    return result
+  }
+}
+
+/** Represents function call output to be returned to the model. */
+public class FunctionResponsePart
+@JvmOverloads
+constructor(
+  public val name: String,
+  public val response: Map<String, Any?>,
+  public val id: String? = null
+) : Part {
+  override fun equals(other: Any?): Boolean {
+    if (this === other) return true
+    if (other !is FunctionResponsePart) return false
+    return name == other.name && response == other.response && id == other.id
+  }
+
+  override fun hashCode(): Int {
+    var result = name.hashCode()
+    result = 31 * result + response.hashCode()
+    result = 31 * result + (id?.hashCode() ?: 0)
+    return result
+  }
+}

ai-logic/firebase-ai-ondevice/CHANGELOG.md

@@ -1,5 +1,7 @@
 # Unreleased
 
+- [feature] Added support for function calling in on-device content generation
+  requests and responses. (#8758)
 - [feature] Added support for multiple `TextPart` and `ImagePart` instances in
   on-device content generation requests. (#8754)