inspector/src/client/index.ts

import { Protocol } from "../shared/protocol.js";
import { Transport } from "../shared/transport.js";
import {
  ClientNotification,
  ClientRequest,
  ClientResult,
  Implementation,
  InitializeResultSchema,
  PROTOCOL_VERSION,
  ServerCapabilities,
} from "../types.js";

/**
 * An MCP client on top of a pluggable transport.
 *
 * The client will automatically begin the initialization flow with the server when connect() is called.
 */
export class Client extends Protocol<
  ClientRequest,
  ClientNotification,
  ClientResult
> {
  private _serverCapabilities?: ServerCapabilities;
  private _serverVersion?: Implementation;

  /**
   * Initializes this client with the given name and version information.
   */
  constructor(private _clientInfo: Implementation) {
    super();
  }

  override async connect(transport: Transport): Promise<void> {
    await super.connect(transport);

    const result = await this.request(
      {
        method: "initialize",
        params: {
          protocolVersion: PROTOCOL_VERSION,
          capabilities: {},
          clientInfo: this._clientInfo,
        },
      },
      InitializeResultSchema,
    );

    if (result === undefined) {
      throw new Error(`Server sent invalid initialize result: ${result}`);
    }

    if (result.protocolVersion !== PROTOCOL_VERSION) {
      throw new Error(
        `Server's protocol version is not supported: ${result.protocolVersion}`,
      );
    }

    this._serverCapabilities = result.capabilities;
    this._serverVersion = result.serverInfo;

    await this.notification({
      method: "notifications/initialized",
    });
  }

  /**
   * After initialization has completed, this will be populated with the server's reported capabilities.
   */
  getServerCapabilities(): ServerCapabilities | undefined {
    return this._serverCapabilities;
  }

  /**
   * After initialization has completed, this will be populated with information about the server's name and version.
   */
  getServerVersion(): Implementation | undefined {
    return this._serverVersion;
  }
}