Before developing your first skill, please read the skill guide.


Follow the Preliminaries and Installation sections from the AEA quick start.

Step 1: Setup

We will first create an AEA and add a scaffold skill, which we call my_search.

aea create my_aea && cd my_aea
aea scaffold skill my_search

In the following steps, we replace the scaffolded Behaviour and Handler in my_aea/skills/my_search with our implementation. We will build a simple skill which lets the AEA send a search query to the OEF and process the resulting response.

Step 2: Develop a Behaviour

A Behaviour class contains the business logic specific to initial actions initiated by the AEA rather than reactions to other events.

In this example, we implement a simple search behaviour. Each time, act() gets called by the main agent loop, we will send a search request to the OEF.

from import Constraint, ConstraintType, Query
from aea.skills.behaviours import TickerBehaviour

from packages.fetchai.protocols.oef.message import OEFMessage
from packages.fetchai.protocols.oef.serialization import DEFAULT_OEF, OEFSerializer

class MySearchBehaviour(TickerBehaviour):
    """This class provides a simple search behaviour."""

    def __init__(self, **kwargs):
        """Initialize the search behaviour."""
        self.sent_search_count = 0

    def setup(self) -> None:
        Implement the setup.

        :return: None
            "[{}]: setting up MySearchBehaviour".format(self.context.agent_name)

    def act(self) -> None:
        Implement the act.

        :return: None
        self.sent_search_count += 1
        search_constraints = [Constraint("country", ConstraintType("==", "UK"))]
        search_query_w_empty_model = Query(search_constraints, model=None)
        search_request = OEFMessage(
            "[{}]: sending search request to OEF, search_count={}".format(
                self.context.agent_name, self.sent_search_count

    def teardown(self) -> None:
        Implement the task teardown.

        :return: None
            "[{}]: tearing down MySearchBehaviour".format(self.context.agent_name)

Searches are proactive and, as such, well placed in a Behaviour. Specifically, we subclass the TickerBehaviour as it allows us to repeatedly search at a defined tick interval.

We place this code in my_aea/skills/my_search/

Step 3: Develop a Handler

So far, we have tasked the AEA with sending search requests to the OEF. However, we have no way of handling the responses sent to the AEA by the OEF at the moment. The AEA would simply respond to the OEF via the default error skill which sends all unrecognised envelopes back to the sender.

Let us now implement a handler to deal with the incoming search responses.

from aea.skills.base import Handler

from packages.fetchai.protocols.oef.message import OEFMessage

class MySearchHandler(Handler):
    """This class provides a simple search handler."""

    SUPPORTED_PROTOCOL = OEFMessage.protocol_id

    def __init__(self, **kwargs):
        """Initialize the handler."""
        self.received_search_count = 0

    def setup(self) -> None:
        """Set up the handler.""""[{}]: setting up MySearchHandler".format(self.context.agent_name))

    def handle(self, message: OEFMessage) -> None:
        Handle the message.

        :param message: the message.
        :return: None
        msg_type = OEFMessage.Type(message.get("type"))

        if msg_type is OEFMessage.Type.SEARCH_RESULT:
            self.received_search_count += 1
            nb_agents_found = len(message.get("agents"))
                "[{}]: found number of agents={}, received search count={}".format(
                    self.context.agent_name, nb_agents_found, self.received_search_count
            "[{}]: number of search requests sent={} vs. number of search responses received={}".format(

    def teardown(self) -> None:
        Teardown the handler.

        :return: None
            "[{}]: tearing down MySearchHandler".format(self.context.agent_name)

We create a handler which is registered for the oef protocol. Whenever it receives a search result, we log the number of agents returned in the search - the agents matching the search query - and update the counter of received searches.

We also implement a trivial check on the difference between the amount of search requests sent and responses received.

Note, how the handler simply reacts to incoming events (i.e. messages). It could initiate further actions, however, they are still reactions to the upstream search event.

Also note, how we have access to other objects in the skill via self.context.

We place this code in my_aea/skills/my_search/

Step 4: Remove unused Task and Model

We have implemented a behaviour and a handler. We could also implement a task and a model, but instead we delete these files in this case, to keep it simple.

We remove the files my_aea/skills/my_search/ and my_aea/skills/my_search/

Step 5: Create the config file

Based on our skill components above, we create the following config file.

name: my_search
author: fetchai
version: 0.1.0
license: Apache-2.0
description: 'A simple search skill utilising the OEF.'
    class_name: MySearchBehaviour
      tick_interval: 5
    class_name: MySearchHandler
    args: {}
models: {}
protocols: ['fetchai/oef:0.1.0']
dependencies: {}

Ensure, you replace the author field with your author name! (Run aea init to set or check the author name.)

Importantly, the keys my_search_behaviour and my_search_handler are used in the above handler to access these skill components at runtime via the context. We also set the tick_interval of the TickerBehaviour to 5 seconds.

We place this code in my_aea/skills/my_search/skill.yaml.

Step 6: Add the oef protocol and connection

Our AEA does not have the oef protocol yet so let's add it.

aea add protocol fetchai/oef:0.1.0

This adds the protocol to our AEA and makes it available on the path packages.fetchai.protocols....

We also need to add the oef connection:

aea add connection fetchai/oef:0.1.0

Step 7: Run a service provider AEA

We first start an oef node (see the connection section for more details) in a separate terminal window.

python scripts/oef/ -c ./scripts/oef/launch_config.json

In order to be able to find another AEA when searching, from a different terminal window, we fetch and run another finished AEA:

aea fetch fetchai/simple_service_registration:0.1.0 && cd simple_service_registration
aea run

This AEA will simply register a location service on the OEF so we can search for it.

Step 8: Run the Search AEA

We can then launch our AEA.

aea run --connections fetchai/oef:0.1.0

We can see that the AEA sends search requests to the OEF and receives search responses from the OEF. Since our AEA is only searching on the OEF - and not registered on the OEF - the search response returns a single agent (the service provider).

We stop the AEA with CTRL + C.

Now it's your turn

We hope this step by step introduction has helped you develop your own skill. We are excited to see what you will build.