Enum Part 

pub enum Part {
    Thinking {
        thinking: String,
        signature: Option<String>,
    },
    Text {
        text: String,
    },
    InlineData {
        mime_type: String,
        data: Vec<u8>,
    },
    FileData {
        mime_type: String,
        file_uri: String,
    },
    FunctionCall {
        name: String,
        args: Value,
        id: Option<String>,
        thought_signature: Option<String>,
    },
    FunctionResponse {
        function_response: FunctionResponseData,
        id: Option<String>,
    },
    ServerToolCall {
        server_tool_call: Value,
    },
    ServerToolResponse {
        server_tool_response: Value,
    },
}

Core traits and types.

Always available regardless of feature flags. Includes:

• Agent - The fundamental trait for all agents
• Tool / Toolset - For extending agents with capabilities
• Session / State - For managing conversation context
• Event - For streaming agent responses
• AdkError / Result - Unified error handling A single part of a Content message.

Parts can be text, binary data, file references, function calls/responses, thinking traces, or server-side tool interactions.

Variants

Thinking

Thinking/reasoning trace from a thinking-capable model.

Must be placed before Text in the enum so that #[serde(untagged)] deserialization matches {"thinking": "..."} before falling through to Text.

Fields

thinking: String

The reasoning/thinking text.

signature: Option<String>

Optional cryptographic signature for thought verification.

Text

Plain text content.

Fields

text: String

The text content.

InlineData

Inline binary data (images, audio, etc.).

Fields

mime_type: String

MIME type of the data.

data: Vec<u8>

Raw binary data.

FileData

File data referenced by URI (URL or cloud storage path).

This allows referencing external files without embedding the data inline. Providers that don’t support URI-based content can fetch and convert to InlineData.

Example

use adk_core::Part;

let image_url = Part::FileData {
    mime_type: "image/jpeg".to_string(),
    file_uri: "https://example.com/image.jpg".to_string(),
};

Fields

mime_type: String

MIME type of the file (e.g., “image/jpeg”, “audio/wav”)

file_uri: String

URI to the file (URL, gs://, etc.)

FunctionCall

A function (tool) call from the model.

Fields

name: String

Name of the function to call.

args: Value

Arguments as a JSON value.

id: Option<String>

Tool call ID for OpenAI-style providers. None for Gemini.

thought_signature: Option<String>

Thought signature for Gemini 3 series models. Must be preserved and relayed back in conversation history during multi-turn function calling.

FunctionResponse

A function (tool) response.

Fields

function_response: FunctionResponseData

The function response data.

id: Option<String>

Tool call ID for OpenAI-style providers. None for Gemini.

ServerToolCall

Server-side tool call data from Gemini 3 built-in tool invocations. Stored as opaque JSON to avoid coupling core types to provider-specific schemas.

Fields

server_tool_call: Value

Opaque JSON payload for the server tool call.

ServerToolResponse

Server-side tool response data from Gemini 3 built-in tool invocations. Stored as opaque JSON to avoid coupling core types to provider-specific schemas.

Fields

server_tool_response: Value

Opaque JSON payload for the server tool response.

Implementations

impl Part

pub fn text(&self) -> Option<&str>

Returns the text content if this is a Text part, None otherwise

pub fn is_thinking(&self) -> bool

Returns true if this part is a Thinking variant

pub fn thinking_text(&self) -> Option<&str>

Returns the thinking text content if this is a Thinking part, None otherwise

pub fn mime_type(&self) -> Option<&str>

Returns the MIME type if this part has one (InlineData or FileData)

pub fn file_uri(&self) -> Option<&str>

Returns the file URI if this is a FileData part

pub fn is_media(&self) -> bool

Returns true if this part contains media (image, audio, video)

pub fn text_part(text: impl Into<String>) -> Part

Create a new text part

pub fn inline_data(mime_type: impl Into<String>, data: Vec<u8>) -> Part

Create a new inline data part

Panics

Panics if data exceeds MAX_INLINE_DATA_SIZE (10 MB).

pub fn file_data( mime_type: impl Into<String>, file_uri: impl Into<String>, ) -> Part

Create a new file data part from URI

Trait Implementations

impl Clone for Part

fn clone(&self) -> Part

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Part

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Part

fn deserialize<__D>( __deserializer: __D, ) -> Result<Part, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Part

fn eq(&self, other: &Part) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Part

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Part