/**
 * Standard error result shape returned from tool handlers when a call fails.
 * Mirrors the MCP `tools/call` error convention: `isError: true` plus a single
 * text content block containing a JSON-encoded payload the calling agent can
 * parse for structured handling.
 */
export interface ToolErrorResult {
    isError: true;
    content: Array<{
        type: 'text';
        text: string;
    }>;
}
export interface ToolErrorPayload {
    code: string;
    message: string;
    [key: string]: unknown;
}
/**
 * Map an unknown error (most often a `UserFacingError` from core) onto the
 * standard tool error result. Unknown error types are reported under the
 * `internal` code with their `.message` (no stack — agents don't need it).
 */
export declare const toMcpError: (err: unknown) => ToolErrorResult;
/**
 * Convenience constructor for the well-known `key_missing` error returned by
 * empirical and latency tools when the required provider env var is unset.
 */
export declare const keyMissingError: (required: string, docs?: string) => ToolErrorResult;
export declare const errorResult: (payload: ToolErrorPayload) => ToolErrorResult;
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