Struct ProtocolError 

pub struct ProtocolError {
    pub code: ProtocolErrorCode,
    pub message: String,
    pub data: Option<Value>,
}

MCP protocol error — becomes a JSON-RPC error response.

Use this for:

• Parse errors
• Invalid requests
• Unknown methods
• Unknown tools (code -32803, NOT -32602)
• Invalid parameters (before the tool is invoked)

Fields

code: ProtocolErrorCode

JSON-RPC error code

message: String

Human-readable error message

data: Option<Value>

Optional structured data

Implementations

impl ProtocolError

pub fn new(code: ProtocolErrorCode, message: impl Into<String>) -> Self

Create a new protocol error

pub fn with_data(self, data: Value) -> Self

Add structured data to the error

pub fn tool_not_found(tool_name: &str) -> Self

Create a “tool not found” error (code -32803)

pub fn invalid_params(message: impl Into<String>) -> Self

Create an “invalid params” error (code -32602)

pub fn parse_error(message: impl Into<String>) -> Self

Create a “parse error” (code -32700)

pub fn method_not_found(method: &str) -> Self

Create a “method not found” error (code -32601)

pub fn is_protocol_error(&self) -> bool

Check if this is a protocol-level error (should be JSON-RPC error)

pub fn json_rpc_code(&self) -> i32

Get the numeric error code for JSON-RPC response

Trait Implementations

impl Clone for ProtocolError

fn clone(&self) -> ProtocolError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ProtocolError

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

Formats the value using the given formatter.

impl Display for ProtocolError

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

Formats the value using the given formatter.

impl Error for ProtocolError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.