AJV TypeScript JSONSchemaType requires methods?

Command.ts

/**
 * Enumeration of valid commands.
 */
export type Command = 'RegisterGame' | 'GameToController' | 'ControllerToGame';

IMessage.ts

import {Server} from "./Server";
import {Command} from "./Command";

export default interface IMessage {
    readonly command: Command;
    // run(server: Server): boolean;
}

MessageA.ts

import IMessage from "./IMessage";
import {Server} from "./Server";

export class MessageA implements IMessage {
    public readonly command = 'RegisterGame';

    /**
     * Code to join the game.
     *
     * @minimum 0
     * @TJS-type integer
     */
    public readonly joinCode: number; // TODO: Restore to constructor but keeping Schema specifiers?

    public constructor(joinCode: number) {
        this.joinCode = joinCode;
    }

    /*
    public run(server: Server): boolean {
        return server.doStuff(this);
    };
    */
}

MessageASchema.ts

import {JSONSchemaType} from "ajv";
import {MessageA} from "./MessageA";
import {Server} from "./Server";

export default class MessageASchema {

    private static readonly SchemaMsgRegisterGame: JSONSchemaType<MessageA> = {
        $id: 'MsgRegisterGame',
        additionalProperties: false,
        properties: {
            command: {
                default: 'RegisterGame',
                enum: ['RegisterGame'],
                type: 'string',
            },
            joinCode: {
                description: 'Code to join the game.',
                minimum: 0,
                type: 'integer',
            },
        },
        required: ['command', 'joinCode'],
        type: 'object',
    };
}

package.json

{
  "name": "ajv-ts-bug-1",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "compile": "tsc",
    "test": "mocha"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "ajv": "^7.0.0-beta.4"
  },
  "devDependencies": {
    "typescript": "^4.0.5",
    "@types/node": "^14.14.7",
    "ts-node": "^9.0.0",
    "typescript-json-schema": "^0.43.0"
  }
}

Server.ts

import IMessage from "./IMessage";

export class Server {
    public doStuff(requestor: IMessage): boolean {
        console.log(`server did stuff for ${requestor}`);
        return true;
    }
}

tsconfig.json

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5",
    "outDir": "./built",
    "sourceMap": true,
    "strict": true,
    "noImplicitAny": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "preserveConstEnums": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  },
  "include": ["src-ts/**/*"],
  "exclude": [
    "node_modules"
  ]
}