#
Build Your Own Pokémon Battle Agent

Now that you’ve explored the potential and limitations of Agentic AI in games, it’s time to get hands-on. In this section, you’ll build your very own AI Agent to battle in Pokémon-style turn-based combat, using everything you’ve learned throughout the course.

We’ll break the system into four key building blocks:

- Poke-env: A Python library designed to train rule-based or reinforcement learning Pokémon bots.

- Pokémon Showdown: An online battle simulator where your agent will fight.

- LLMAgentBase: A custom Python class we’ve built to connect your LLM with the Poke-env battle environment.

- TemplateAgent: A starter template you’ll complete to create your own unique battle agent.

Let’s explore each of these components in more detail.

##
🧠 Poke-env

Poke-env is a Python interface originally built for training reinforcement learning bots by Haris Sahovic, but we’ve repurposed it for Agentic AI.
It allows your agent to interact with Pokémon Showdown through a simple API.

It provides a `Player` class from which your Agent will inherit, covering everything needed to communicate with the graphical interface.

Documentation: poke-env.readthedocs.io
Repository: github.com/hsahovic/poke-env

##
⚔️ Pokémon Showdown

Pokémon Showdown is an open-source battle simulator where your agent will play live Pokémon battles.
It provides a full interface to simulate and display battles in real time. In our challenge, your bot will act just like a human player, choosing moves turn by turn.

We’ve deployed a server that all participants will use to battle. Let’s see who builds the best AI battle Agent!

Repository: github.com/smogon/Pokemon-Showdown
Website: pokemonshowdown.com

##
🔌 LLMAgentBase

`LLMAgentBase` is a Python class that extends the `Player` class from Poke-env.
It serves as the bridge between your LLM and the Pokémon battle simulator, handling input/output formatting and maintaining battle context.

This base agent provides a set of tools (defined in `STANDARD_TOOL_SCHEMA`) to interact with the environment, including:

- `choose_move`: for selecting an attack during battle
- `choose_switch`: for switching Pokémon

The LLM should use these tools to make decisions during a match.

###
🧠 Core Logic

- `choose_move(battle: Battle)`: This is the main method invoked each turn. It takes a `Battle` object and returns an action string based on the LLM’s output.

###
🔧 Key Internal Methods

- `_format_battle_state(battle)`: Converts the current battle state into a string, making it suitable for sending to the LLM.

- `_find_move_by_name(battle, move_name)`: Finds a move by name, used in LLM responses that call `choose_move`.

- `_find_pokemon_by_name(battle, pokemon_name)`: Locates a specific Pokémon to switch into, based on the LLM’s switch command.

- `_get_llm_decision(battle_state)`: This method is abstract in the base class. You’ll need to implement it in your own agent (see next section), where you define how to query the LLM and parse its response.

Here’s an excerpt showing how that decision-making works:

    STANDARD_TOOL_SCHEMA = {
        "choose_move": {
            ...
        },
        "choose_switch": {
            ...
        },
    }

    class LLMAgentBase(Player):
        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            self.standard_tools = STANDARD_TOOL_SCHEMA
            self.battle_history = []

        def _format_battle_state(self, battle: Battle) -> str:
            active_pkmn = battle.active_pokemon
            active_pkmn_info = f"Your active Pokemon: {active_pkmn.species} " \
                               f"(Type: {'/'.join(map(str, active_pkmn.types))}) " \
                               f"HP: {active_pkmn.current_hp_fraction * 100:.1f}% " \
                               f"Status: {active_pkmn.status.name if active_pkmn.status else 'None'} " \
                               f"Boosts: {active_pkmn.boosts}"

            opponent_pkmn = battle.opponent_active_pokemon
            opp_info_str = "Unknown"
            if opponent_pkmn:
                opp_info_str = f"{opponent_pkmn.species} " \
                               f"(Type: {'/'.join(map(str, opponent_pkmn.types))}) " \
                               f"HP: {opponent_pkmn.current_hp_fraction * 100:.1f}% " \
                               f"Status: {opponent_pkmn.status.name if opponent_pkmn.status else 'None'} " \
                               f"Boosts: {opponent_pkmn.boosts}"
            opponent_pkmn_info = f"Opponent's active Pokemon: {opp_info_str}"

            available_moves_info = "Available moves:\n"
            if battle.available_moves:
                available_moves_info += "\n".join(
                    [f"- {move.id} (Type: {move.type}, BP: {move.base_power}, Acc: {move.accuracy}, PP: {move.current_pp}/{move.max_pp}, Cat: {move.category.name})"
                     for move in battle.available_moves]
                )
            else:
                 available_moves_info += "- None (Must switch or Struggle)"

            available_switches_info = "Available switches:\n"
            if battle.available_switches:
                  available_switches_info += "\n".join(
                      [f"- {pkmn.species} (HP: {pkmn.current_hp_fraction * 100:.1f}%, Status: {pkmn.status.name if pkmn.status else 'None'})"
                       for pkmn in battle.available_switches]
                  )
            else:
                available_switches_info += "- None"

            state_str = f"{active_pkmn_info}\n" \
                        f"{opponent_pkmn_info}\n\n" \
                        f"{available_moves_info}\n\n" \
                        f"{available_switches_info}\n\n" \
                        f"Weather: {battle.weather}\n" \
                        f"Terrains: {battle.fields}\n" \
                        f"Your Side Conditions: {battle.side_conditions}\n" \
                        f"Opponent Side Conditions: {battle.opponent_side_conditions}"
            return state_str.strip()

        def _find_move_by_name(self, battle: Battle, move_name: str) -> Optional[Move]:
            normalized_name = normalize_name(move_name)
            # Prioritize exact ID match
            for move in battle.available_moves:
                if move.id == normalized_name:
                    return move
            # Fallback: Check display name (less reliable)
            for move in battle.available_moves:
                if move.name.lower() == move_name.lower():
                    print(f"Warning: Matched move by display name '{move.name}' instead of ID '{move.id}'. Input was '{move_name}'.")
                    return move
            return None

        def _find_pokemon_by_name(self, battle: Battle, pokemon_name: str) -> Optional[Pokemon]:
            normalized_name = normalize_name(pokemon_name)
            for pkmn in battle.available_switches:
                # Normalize the species name for comparison
                if normalize_name(pkmn.species) == normalized_name:
                    return pkmn
            return None

        async def choose_move(self, battle: Battle) -> str:
            battle_state_str = self._format_battle_state(battle)
            decision_result = await self._get_llm_decision(battle_state_str)
            print(decision_result)
            decision = decision_result.get("decision")
            error_message = decision_result.get("error")
            action_taken = False
            fallback_reason = ""

            if decision:
                function_name = decision.get("name")
                args = decision.get("arguments", {})
                if function_name == "choose_move":
                    move_name = args.get("move_name")
                    if move_name:
                        chosen_move = self._find_move_by_name(battle, move_name)
                        if chosen_move and chosen_move in battle.available_moves:
                            action_taken = True
                            chat_msg = f"AI Decision: Using move '{chosen_move.id}'."
                            print(chat_msg)
                            return self.create_order(chosen_move)
                        else:
                            fallback_reason = f"LLM chose unavailable/invalid move '{move_name}'."
                    else:
                         fallback_reason = "LLM 'choose_move' called without 'move_name'."
                elif function_name == "choose_switch":
                    pokemon_name = args.get("pokemon_name")
                    if pokemon_name:
                        chosen_switch = self._find_pokemon_by_name(battle, pokemon_name)
                        if chosen_switch and chosen_switch in battle.available_switches:
                            action_taken = True
                            chat_msg = f"AI Decision: Switching to '{chosen_switch.species}'."
                            print(chat_msg)
                            return self.create_order(chosen_switch)
                        else:
                            fallback_reason = f"LLM chose unavailable/invalid switch '{pokemon_name}'."
                    else:
                        fallback_reason = "LLM 'choose_switch' called without 'pokemon_name'."
                else:
                    fallback_reason = f"LLM called unknown function '{function_name}'."

            if not action_taken:
                if not fallback_reason:
                     if error_message:
                         fallback_reason = f"API Error: {error_message}"
                     elif decision is None:
                          fallback_reason = "LLM did not provide a valid function call."
                     else:
                          fallback_reason = "Unknown error processing LLM decision."

                print(f"Warning: {fallback_reason} Choosing random action.")

                if battle.available_moves or battle.available_switches:
                     return self.choose_random_move(battle)
                else:
                     print("AI Fallback: No moves or switches available. Using Struggle/Default.")
                     return self.choose_default_move(battle)

        async def _get_llm_decision(self, battle_state: str) -> Dict[str, Any]:
            raise NotImplementedError("Subclasses must implement _get_llm_decision")

Full source code: agents.py

##
🧪 TemplateAgent

Now comes the fun part! With LLMAgentBase as your foundation, it’s time to implement your own agent, with your own strategy to climb the leaderboard.

You’ll start from this template and build your own logic. We’ve also provided three complete examples using OpenAI, Mistral, and Gemini models to guide you.

Here’s a simplified version of the template:

    class TemplateAgent(LLMAgentBase):
        """Uses Template AI API for decisions."""
        def __init__(self, api_key: str = None, model: str = "model-name", *args, **kwargs):
            super().__init__(*args, **kwargs)
            self.model = model
            self.template_client = TemplateModelProvider(api_key=...)
            self.template_tools = list(self.standard_tools.values())

        async def _get_llm_decision(self, battle_state: str) -> Dict[str, Any]:
            """Sends state to the LLM and gets back the function call decision."""
            system_prompt = (
                "You are a ..."
            )
            user_prompt = f"..."

            try:
                response = await self.template_client.chat.completions.create(
                    model=self.model,
                    messages=[
                        {"role": "system", "content": system_prompt},
                        {"role": "user", "content": user_prompt},
                    ],
                )
                message = response.choices[0].message

                return {"decision": {"name": function_name, "arguments": arguments}}

            except Exception as e:
                print(f"Unexpected error during call: {e}")
                return {"error": f"Unexpected error: {e}"}

This code won’t run out of the box, it’s a blueprint for your custom logic.

With all the pieces ready, it’s your turn to build a competitive agent. In the next section, we’ll show how to deploy your agent to our server and battle others in real-time.

Let the battle begin! 🔥

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