Enum ContentBlock 

pub enum ContentBlock {
    Text(TextContent),
    Image(ImageContent),
    Audio(AudioContent),
    ResourceLink(ResourceLink),
    Resource(EmbeddedResource),
}

Content blocks represent displayable information in the Agent Client Protocol.

They provide a structured way to handle various types of user-facing content—whether it’s text from language models, images for analysis, or embedded resources for context.

Content blocks appear in:

• User prompts sent via session/prompt
• Language model output streamed through session/update notifications
• Progress updates and results from tool calls

This structure is compatible with the Model Context Protocol (MCP), enabling agents to seamlessly forward content from MCP tool outputs without transformation.

See protocol docs: Content

Variants

Text(TextContent)

Plain text content

All agents MUST support text content blocks in prompts.

Image(ImageContent)

Images for visual context or analysis.

Requires the image prompt capability when included in prompts.

Audio(AudioContent)

Audio data for transcription or analysis.

Requires the audio prompt capability when included in prompts.

ResourceLink(ResourceLink)

References to resources that the agent can access.

All agents MUST support resource links in prompts.

Resource(EmbeddedResource)

Complete resource contents embedded directly in the message.

Preferred for including context as it avoids extra round-trips.

Requires the embeddedContext prompt capability when included in prompts.

Trait Implementations

impl Clone for ContentBlock

fn clone(&self) -> ContentBlock

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ContentBlock

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ContentBlock

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T: Into<String>> From<T> for ContentBlock

fn from(value: T) -> Self

Converts to this type from the input type.

impl JsonSchema for ContentBlock

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for ContentBlock

fn eq(&self, other: &ContentBlock) -> 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 ContentBlock

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ContentBlock