Struct CallToolResult 

pub struct CallToolResult {
    pub content: Vec<ContentBlock>,
    pub is_error: Option<bool>,
    pub meta: Option<Map<String, Value>>,
    pub structured_content: Option<Map<String, Value>>,
}

The server’s response to a tool call.

JSON schema

{
 "description": "The server's response to a tool call.",
 "type": "object",
 "required": [
   "content"
 ],
 "properties": {
   "_meta": {
     "description": "See [General fields: _meta](https://modelcontextprotocol.io/specification/2025-11-25/basic/index#meta) for notes on _meta usage.",
     "type": "object",
     "additionalProperties": {}
   },
   "content": {
     "description": "A list of content objects that represent the unstructured result of the tool call.",
     "type": "array",
     "items": {
       "$ref": "#/$defs/ContentBlock"
     }
   },
   "isError": {
     "description": "Whether the tool call ended in an error.\n\nIf not set, this is assumed to be false (the call was successful).\n\nAny errors that originate from the tool SHOULD be reported inside the result\nobject, with isError set to true, _not_ as an MCP protocol-level error\nresponse. Otherwise, the LLM would not be able to see that an error occurred\nand self-correct.\n\nHowever, any errors in _finding_ the tool, an error indicating that the\nserver does not support tool calls, or any other exceptional conditions,\nshould be reported as an MCP error response.",
     "type": "boolean"
   },
   "structuredContent": {
     "description": "An optional JSON object that represents the structured result of the tool call.",
     "type": "object",
     "additionalProperties": {}
   }
 }
}

Fields

content: Vec<ContentBlock>

A list of content objects that represent the unstructured result of the tool call.

is_error: Option<bool>

Whether the tool call ended in an error. If not set, this is assumed to be false (the call was successful). Any errors that originate from the tool SHOULD be reported inside the result object, with isError set to true, not as an MCP protocol-level error response. Otherwise, the LLM would not be able to see that an error occurred and self-correct. However, any errors in finding the tool, an error indicating that the server does not support tool calls, or any other exceptional conditions, should be reported as an MCP error response.

meta: Option<Map<String, Value>>

See General fields: _meta for notes on _meta usage.

structured_content: Option<Map<String, Value>>

An optional JSON object that represents the structured result of the tool call.

Implementations

impl CallToolResult

pub fn text_content(content: Vec<TextContent>) -> Self

pub fn image_content(content: Vec<ImageContent>) -> Self

pub fn audio_content(content: Vec<AudioContent>) -> Self

pub fn resource_link(content: Vec<ResourceLink>) -> Self

pub fn embedded_resource(content: Vec<EmbeddedResource>) -> Self

pub fn with_error(error: CallToolError) -> Self

Create a CallToolResult with an error, containing an error message in the content

pub fn with_meta(self, meta: Option<Map<String, Value>>) -> Self

Assigns metadata to the CallToolResult, enabling the inclusion of extra context or details.

pub fn with_structured_content( self, structured_content: Map<String, Value>, ) -> Self

Assigns structured_content to the CallToolResult

pub fn from_content(content: Vec<ContentBlock>) -> Self

Creates a new instance using the provided content blocks.

This method initializes the structure with the given content and resets all optional fields (is_error, meta, and structured_content) to None.

Arguments

• content - A vector of ContentBlock values to populate the instance.

Returns

Returns a new instance containing the supplied content.

pub fn add_content(self, content: ContentBlock) -> Self

Adds a single content block to the instance.

This method appends the provided content to the existing content vector and returns the updated instance, enabling a builder-style pattern.

Trait Implementations

impl Clone for CallToolResult

fn clone(&self) -> CallToolResult

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CallToolResult

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for CallToolResult

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<CallToolError> for CallToolResult

Conversion of CallToolError into a CallToolResult with an error.

fn from(value: CallToolError) -> Self

Converts to this type from the input type.

impl From<CallToolResult> for MessageFromServer

fn from(value: CallToolResult) -> Self

Converts to this type from the input type.

impl From<CallToolResult> for GenericResult

fn from(value: CallToolResult) -> Self

Converts to this type from the input type.

impl From<CallToolResult> for ResultFromServer

fn from(value: CallToolResult) -> Self

Converts to this type from the input type.

impl From<CallToolResult> for ServerResult

fn from(value: CallToolResult) -> Self

Converts to this type from the input type.

impl Serialize for CallToolResult

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl TryFrom<ResultFromServer> for CallToolResult

type Error = RpcError

The type returned in the event of a conversion error.

fn try_from(value: ResultFromServer) -> Result<Self, Self::Error>

Performs the conversion.