export interface McpLogger {
info: (...args: unknown[]) => void;
warn: (...args: unknown[]) => void;
error: (...args: unknown[]) => void;
}
/**
* Creates a logger that writes to stderr only.
*
* IMPORTANT: MCP uses stdio for JSON-RPC communication. The server sends
* JSON responses over stdout, and the client parses them. Any non-JSON
* output to stdout (like console.log) will corrupt the protocol and cause
* parsing errors like "invalid character 'M' looking for beginning of value".
*
* All logging MUST go to stderr to avoid interfering with MCP communication.
*/
export function createMcpLogger(scope: string): McpLogger {
return {
info: (...args: unknown[]): void => {
// Use console.error (stderr) instead of console.log (stdout)
// to avoid corrupting MCP's JSON-RPC protocol on stdout
console.error('[MCP][' + scope + '][INFO]', ...args);
},
warn: (...args: unknown[]): void => {
console.error('[MCP][' + scope + '][WARN]', ...args);
},
error: (...args: unknown[]): void => {
console.error('[MCP][' + scope + '][ERROR]', ...args);
},
};
}
