Function jsonRpcErrorBody

packages/hosts/mcp/src/envelope.ts:103–140

(
  status: number,
  code: number,
  message: string,
  opts?: {
    readonly cors?: boolean;
    readonly challenge?: string;
    readonly retryAfterSeconds?: number;
    /**
     * The id to echo. Envelope-level errors have no request to answer and stay
     * at the default `null`; only an error that answers ONE identified JSON-RPC
     * request (the pre-initialize guard below) sets it, since a client matches
     * the response to its pending request by id.
     */
    readonly id?: string | number | null;
  },
)

 * local — the four hand-rolled copies are deleted in favor of this.
 */
export const jsonRpcErrorBody = (
  status: number,
  code: number,
  message: string,
  opts?: {
    readonly cors?: boolean;
    readonly challenge?: string;
    readonly retryAfterSeconds?: number;
    /**
     * The id to echo. Envelope-level errors have no request to answer and stay
     * at the default `null`; only an error that answers ONE identified JSON-RPC
     * request (the pre-initialize guard below) sets it, since a client matches
     * the response to its pending request by id.
     */
    readonly id?: string | number | null;
  },
): Response => {
  const cors = opts?.cors ?? true;
  const challenge = opts?.challenge;
  const retryAfterSeconds = opts?.retryAfterSeconds;
  return new Response(
    JSON.stringify({ jsonrpc: "2.0", error: { code, message }, id: opts?.id ?? null }),
    {
      status,
      headers: {
        "content-type": "application/json",
        ...(cors ? { "access-control-allow-origin": "*" } : {}),
        ...(challenge
          ? {
              "www-authenticate": challenge,
              "access-control-expose-headers": "WWW-Authenticate",
            }
          : {}),
        ...(retryAfterSeconds === undefined ? {} : { "retry-after": String(retryAfterSeconds) }),
      },
    },
  );
};

/**
 * Advertised on transient-auth 503s (`Unavailable` outcomes) so clients back