/**
 * @fileoverview Blank optional inputs read as omitted. Form-based clients send `""` for a field
 * nobody filled in, so a blank or whitespace-only string carries no search intent: sent as-is,
 * Crossref ignores a blank `query`, matches nothing on a blank field query, and rejects or
 * arbitrarily applies a blank filter value. Every search handler normalizes its optional strings
 * through here once, at the top, so each guard below it reads the value the request will carry.
 * @module mcp-server/tools/blank-input
 */
/**
 * The value, or `undefined` when it is absent, empty, or whitespace only. A non-blank value is
 * returned exactly as supplied — nothing is trimmed off it.
 */
export declare function nonBlank<T extends string>(value: T | undefined): Exclude<T, ''> | undefined;
/** Whether a string input was supplied but carried nothing — the case `nonBlank` drops. */
export declare function isBlank(value: string | undefined): boolean;
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