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🔌 How to write a plugin

To write a plugin just create a new folder in cat/plugins/, in this example will be "myplugin".

You need two files to your plugin folder:

├── cat/
│   ├── plugins/
|   |   ├── myplugin/
|   |   |   ├──
|   |   |   ├── plugin.json

The plugin.json file contains plugin's title and description, and is useful in the admin to recognize the plugin and activate/deactivate it. If your plugin does not contain a plugin.json the cat will not block your plugin, but it is useful to have it.

plugin.json example:

    "name": "The name of my plugin",
    "description": "Short description of my plugin"

Now let's start with a little import:

from cat.mad_hatter.decorators import tool, hook

You are now ready to change the Cat's behavior using Tools and Hooks.

🧰 Tools

Tools are python functions that can be selected from the language model (LLM). Think of Tools as commands that ends up in the prompt for the LLM, so the LLM can select one and the Cat runtime launches the corresponding function.
Here is an example of Tool to let the Cat tell you what time it is:

def get_the_time(tool_input, cat):
    """Replies to "what time is it", "get the clock" and similar questions. Input is always None.."""

    return str(

More examples on tools here.

🪝 Hooks

Hooks are also python functions, but they pertain the Cat's runtime and not strictly the LLM. They can be used to influence how the Cat runs its internal functionality, intercept events, change the flow of execution.

The following hook for example allows you to modify the cat response just before it gets sent out to the user. In this case we make a "grumpy rephrase" of the original response.

def before_cat_sends_message(message, cat):

    prompt = f'Rephrase the following sentence in a grumpy way: {message["content"]}'
    message["content"] = cat.llm(prompt)

    return message

If you want to change the default Agent behavior you can start overriding the default plugin hooks, located in /core/cat/mad_hatter/core_plugin/hooks/, rewriting them in the plugin file with a higher priority. Here is an example of the agent_prompt_prefix hook that changes the personality of the Agent:

# Original Hook, from /core/cat/mad_hatter/core_plugin/hooks/

def agent_prompt_prefix(prefix, cat):
    prefix = """You are the Cheshire Cat AI, an intelligent AI that passes the Turing test.
                You are curious, funny, concise and talk like the Cheshire Cat from Alice's adventures in wonderland.
                You answer Human using tools and context."""
# Modified Hook, to be copied into

@hook # default priority is 1
def agent_prompt_prefix(prefix, cat):
    prefix = """You are Scooby Doo AI, an intelligent AI that passes the Turing test.
                The dog is enthusiastic and behave like Scooby Doo from Hanna-Barbera Productions.
                You answer Human using tools and context."""
    return prefix

Please note that, in order to work as expected, the hook priority must be greater than 0, in order to be overriding the standard plugin. If you do not provide a priority, your hook will have priority=1 and implicitly override the default one.

More examples on hooks here.

📋 Forms

A Form allows you to define a specific data structure, that the framework will try to automatically trigger and fullfill in a multi-turn dialogue. You can define custom:

  • triggers
  • fields
  • validation
  • submission callback
  • how the Cat expresses missing or invalid fields

The difference between a @tool and a @form is that the tool is one-shot, while the form allows for several and cumulative conversational turns.
Imagine a Cat @form as the common HTML <form>, but on a conversational level.

Here is an example for a pizza order:

from pydantic import BaseModel
from cat.experimental.form import form, CatForm

# data structure to fill up
class PizzaOrder(BaseModel):
    pizza_type: str
    phone: int

# forms let you control goal oriented conversations
class PizzaForm(CatForm):
    description = "Pizza Order"
    model_class = PizzaOrder
    start_examples = [
        "order a pizza!",
        "I want pizza"
    stop_examples = [
        "stop pizza order",
        "not hungry anymore",
    ask_confirm = True

    def submit(self, form_data):

        # do the actual order here!

        # return to convo
        return {
            "output": f"Pizza order on its way: {form_data}"

More examples on forms here.