Documentation / @agentick/mcp / protocolError

Function: protocolError()

protocolError(code, message, data?): never

Defined in: protocol/errors.ts:130

Throw-shape for JSON-RPC protocol errors emitted from server handlers.

SDK quirk: new McpError(code, message) calls super("MCP error {code}: {message}"), meaning error.message carries a prefix at construction time. The SDK serialization layer then ships error.message verbatim, and the receiving client SDK reconstructs an McpError adding ANOTHER prefix — yielding a doubled "MCP error -32601: MCP error -32601: ..." in the client's caught error.

protocolError sidesteps this by throwing a plain Error with code and data properties on it. The SDK's error serialization at shared/protocol.js reads error['code'] and error.message directly (no instanceof check on McpError), so the client receives a clean message and the client SDK adds exactly one prefix.

Parameters

code

number

message

string

data?

unknown

Returns

never