Enum McpError 

pub enum McpError {
    Transport(String),
    Protocol(String),
    Serialization(String),
    InvalidUri(String),
    ToolNotFound(String),
    ResourceNotFound(String),
    PromptNotFound(String),
    MethodNotFound(String),
    UnsupportedProtocolVersion {
        requested: String,
        supported: Vec<String>,
    },
    HeaderMismatch(String),
    MissingRequiredClientCapability(Value),
    InvalidParams(String),
    Connection(String),
    Authentication(String),
    Auth(String),
    Forbidden(String),
    RateLimited {
        retry_after_ms: u64,
    },
    Validation(String),
    Io(String),
    Url(String),
    Http(String),
    WebSocket(String),
    SchemaValidation(String),
    Timeout(String),
    Cancelled(String),
    Internal(String),
}

The main error type for the MCP SDK

Variants

Transport(String)

Transport-related errors (connection, I/O, etc.)

Protocol(String)

Protocol-level errors (invalid messages, unexpected responses, etc.)

Serialization(String)

JSON serialization/deserialization errors

InvalidUri(String)

Invalid URI format or content

ToolNotFound(String)

Requested tool was not found

ResourceNotFound(String)

Requested resource was not found

PromptNotFound(String)

Requested prompt was not found

MethodNotFound(String)

Method not found (JSON-RPC error)

UnsupportedProtocolVersion

Requested MCP protocol revision is not supported by the peer.

Fields

requested: String

supported: Vec<String>

HeaderMismatch(String)

Standard MCP HTTP headers do not match the JSON-RPC body.

MissingRequiredClientCapability(Value)

A modern request omitted a capability required by the operation.

InvalidParams(String)

Invalid parameters (JSON-RPC error)

Connection(String)

Connection-related errors

Authentication(String)

Authentication/authorization errors

Auth(String)

OAuth 2.1 authorization errors

Forbidden(String)

The authenticated principal is not allowed to perform the operation.

RateLimited

The caller exceeded an enforced request rate.

Fields

retry_after_ms: u64

Validation(String)

Input validation errors

Io(String)

I/O errors from the standard library

Url(String)

URL parsing errors

Http(String)

HTTP-related errors when using HTTP transport

WebSocket(String)

WebSocket-related errors when using WebSocket transport

SchemaValidation(String)

JSON Schema validation errors

Timeout(String)

Timeout errors

Cancelled(String)

Cancellation errors

Internal(String)

Internal errors that shouldn’t normally occur

Implementations

impl McpError

pub fn transport<S: Into<String>>(message: S) -> Self

Create a new transport error

pub fn protocol<S: Into<String>>(message: S) -> Self

Create a new protocol error

pub fn validation<S: Into<String>>(message: S) -> Self

Create a new validation error

pub fn connection<S: Into<String>>(message: S) -> Self

Create a new connection error

pub fn internal<S: Into<String>>(message: S) -> Self

Create a new internal error

pub fn io(err: Error) -> Self

Create a new IO error from std::io::Error

pub fn serialization(err: Error) -> Self

Create a new serialization error from serde_json::Error

pub fn timeout<S: Into<String>>(message: S) -> Self

Create a new timeout error

pub fn connection_error<S: Into<String>>(message: S) -> Self

Create a connection error (compatibility method)

pub fn protocol_error<S: Into<String>>(message: S) -> Self

Create a protocol error (compatibility method)

pub fn validation_error<S: Into<String>>(message: S) -> Self

Create a validation error (compatibility method)

pub fn timeout_error() -> Self

Create a timeout error (compatibility method)

pub fn is_recoverable(&self) -> bool

Check if this error is recoverable

pub fn category(&self) -> &'static str

Get the error category for logging/metrics

impl McpError

pub async fn log_with_context(&self, context: ErrorContext)

Log this error with structured context

pub async fn log_error(&self, operation: &str)

Log this error with basic context

Trait Implementations

impl Clone for McpError

fn clone(&self) -> McpError

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for McpError

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

Formats the value using the given formatter.

impl Display for McpError

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

Formats the value using the given formatter.

impl Error for McpError

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.

impl From<&McpError> for ErrorLogLevel

fn from(error: &McpError) -> Self

Converts to this type from the input type.

impl From<AuthError> for McpError

Convert AuthError to McpError

fn from(err: AuthError) -> Self

Converts to this type from the input type.

impl From<Error> for McpError

fn from(err: Error) -> Self

Converts to this type from the input type.

impl From<Error> for McpError

fn from(err: Error) -> Self

Converts to this type from the input type.

impl From<Error> for McpError

Available on crate feature http only.

fn from(err: Error) -> Self

Converts to this type from the input type.

impl From<Error> for McpError

Available on crate feature websocket only.

fn from(err: Error) -> Self

Converts to this type from the input type.

impl From<ParseError> for McpError

fn from(err: ParseError) -> Self

Converts to this type from the input type.

impl From<PluginError> for McpError

fn from(err: PluginError) -> Self

Converts to this type from the input type.