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 [specification/2025-06-18/basic/index#general-fields] 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": "#/definitions/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 [specification/2025-06-18/basic/index#general-fields] for notes on _meta usage.

structured_content: Option<Map<String, Value>>

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

Trait Implementations

impl Clone for CallToolResult

fn clone(&self) -> CallToolResult

Returns a duplicate of the value.

const 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<CallToolResult> for MessageFromServer

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 FromMessage<CallToolResult> for ServerMessage

fn from_message( message: CallToolResult, request_id: Option<RequestId>, ) -> Result<Self, RpcError>

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 ToMessage<ServerMessage> for CallToolResult

fn to_message( self, request_id: Option<RequestId>, ) -> Result<ServerMessage, RpcError>

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.