/**
 * ExternalMcpServer — manages one externally-spawned MCP server subprocess.
 *
 * Lifecycle:
 *   - start(): spawn child via SDK StdioClientTransport, perform MCP handshake.
 *   - listTools(): return tool descriptors from the server (cached after first call).
 *   - callTool(name, args): invoke a tool, return its result.
 *   - stop(): SIGTERM the child, wait up to 5s, SIGKILL if still alive.
 *
 * SECURITY: providerConfig.mcpEnv may contain API tokens. NEVER include the
 * env contents in error messages, log lines, or returned errors. Only the
 * provider NAME is safe to expose externally.
 *
 * Error isolation: ExternalMcpServer does NOT implement circuit-breaker or
 * restart-on-crash logic. Observability MCPs are best-effort — a crashed
 * provider is simply absent from the diagnoser's tool list for that spawn.
 * The caller (mergeObsTools) uses Promise.allSettled to handle partial failure.
 */
import type { ObservabilityProvider } from "../config/schema.js";
export interface ToolDescriptor {
    name: string;
    description?: string;
    inputSchema?: unknown;
}
export declare class ExternalMcpServer {
    private readonly provider;
    private client;
    private transport;
    private toolsCache;
    private stopping;
    constructor(provider: ObservabilityProvider);
    get name(): string;
    start(): Promise<void>;
    listTools(): Promise<ToolDescriptor[]>;
    callTool(name: string, args: unknown): Promise<unknown>;
    stop(): Promise<void>;
}
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