Enum McpError 

#[non_exhaustive]
pub enum McpError {
    Connect {
        server: String,
        message: String,
    },
    ListTools {
        server: String,
        message: String,
    },
    InvalidPayload(String),
    CallTool {
        server: String,
        tool: String,
        message: String,
    },
}

Assembly-time errors (connect / list tools); call-time errors go through ToolError::Execution.

Callers usually only handle this error at assembly time; tool execution failures are relayed back to the model as text by the agent loop without aborting the loop.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Connect

Child process startup failure / invalid or unreachable URL / protocol handshake failure; carries the server name to identify the target in multi-server setups.

Fields

server: String

The target server name (the server_name passed at construction).

message: String

Failure reason.

ListTools

Listing tools failed (protocol-level error); carries the server name.

Fields

server: String

The target server name (the server_name passed at construction).

message: String

Failure reason.

InvalidPayload(String)

MCP effect payload is malformed or not an MCP request.

CallTool

Calling an MCP tool failed at protocol/transport level.

Fields

server: String

Target server id.

tool: String

Raw tool name.

message: String

Failure reason.

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<(), Error>

Formats the value using the given formatter.

impl Display for McpError

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

Formats the value using the given formatter.

impl Eq for McpError

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 PartialEq for McpError

fn eq(&self, other: &McpError) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for McpError