Tool Filter MCP

import { FilteredTool } from './types.js'; export interface UpstreamTimeouts { connection: number; toolList: number; } export interface MCPClient { connect(): Promise<void>; listTools(): Promise<{ tools: FilteredTool[] }>; callTool(name: string, args: Record<string, unknown>): Promise<unknown>; disconnect(): void; isConnected(): boolean; } export class UpstreamConnection { private identifier: string; private client: MCPClient; private timeouts: UpstreamTimeouts; private connected: boolean = false; private toolCache: FilteredTool[] | null = null; constructor( identifier: string, client: MCPClient, timeouts: UpstreamTimeouts = { connection: 30000, toolList: 10000 } ) { this.identifier = identifier; this.client = client; this.timeouts = timeouts; } async connect(): Promise<void> { if (this.connected) { throw new Error('Already connected'); } try { await this.withTimeout(this.client.connect(), this.timeouts.connection, 'Connection timeout'); this.connected = true; } catch (error) { this.connected = false; throw error; } } async fetchTools(): Promise<FilteredTool[]> { if (!this.connected) { throw new Error('Not connected'); } if (this.toolCache !== null) { return this.toolCache; } try { const response = await this.withTimeout( this.client.listTools(), this.timeouts.toolList, 'Tool list fetch timeout' ); this.toolCache = response.tools; return this.toolCache; } catch (error) { throw error; } } async callTool(name: string, args: Record<string, unknown>): Promise<unknown> { if (!this.connected) { throw new Error('Not connected'); } return await this.client.callTool(name, args); } disconnect(): void { if (this.connected) { this.client.disconnect(); this.connected = false; } } isConnected(): boolean { return this.connected && this.client.isConnected(); } getIdentifier(): string { return this.identifier; } getCachedTools(): FilteredTool[] | null { return this.toolCache; } private async withTimeout<T>( promise: Promise<T>, timeoutMs: number, errorMessage: string ): Promise<T> { let timeoutHandle: NodeJS.Timeout; const timeoutPromise = new Promise<never>((_, reject) => { timeoutHandle = setTimeout(() => { reject(new Error(`${errorMessage} after ${timeoutMs}ms`)); }, timeoutMs); }); try { const result = await Promise.race([promise, timeoutPromise]); clearTimeout(timeoutHandle!); return result; } catch (error) { clearTimeout(timeoutHandle!); throw error; } } }