Developing on the API

The FlexMeasures API is the main way that third-parties can automate their interaction with FlexMeasures, so it’s highly important.

This is a small guide for creating new versions of the API and its docs.


This guide was written for API versions below v3.0 and is currently out of date.


A guide for endpoint design, e.g. using Marshmallow schemas and common validators.

Introducing a new API version

Larger changes to the API, other than fixes and refactoring, should be done by creating a new API version. In the guide we’re assuming the new version is v1.1.

Whether we need a new API version or not, doesn’t have a clear set of rules yet. Certainly backward-incompatible changes should require one, but as you’ll see, there is also certain overhead in creating a new version, so a careful trade-off is advised.


For the rest of this guide we’ll assume your new API version is v1_1.

Set up new module with routes

In flexmeasures/api create a new module (folder with Copy over the from the previous API version. By default we import all routes from the previous version:

from flexmeasures.api.v1 import routes as v1_routes, implementations as v1_implementations

Set the service listing for this version (or overwrite completely if needed):

v1_1_service_listing = copy.deepcopy(v1_routes.v1_service_listing)
v1_1_service_listing["version"] = "1.1"

Then update and redecorate each API endpoint as follows:

@flexmeasures_api.route("/getService", methods=["GET"])
def get_service():
    return v1_implementations.get_service_response(v1_1_service_listing)

Set up a new blueprint

In the new module’s flexmeasures/api/v1_1/__init.py__, copy the contents of flexmeasures/api/v1/__init.py__ (previous API version). Change all references to the version name in the new file (for example: flexmeasures_api_v1 should become flexmeasures_api_v1_1).

In flexmeasures/api/ update the version listing in get_versions() and register a blueprint for the new api version by adding:

from flexmeasures.api.v1_1 import register_at as v1_1_register_at

New or updated endpoint implementations

Write functionality of new or updated endpoints in:


Utility functions that are commonly shared between endpoint implementations of different versions should go in:


where we distinguish between response decorators, request validators and other utils.


If you changed an endpoint in the new version, write a test for it. Usually, there is no need to copy the tests for unchanged endpoints, if not a major API version is being released.

Test the entire api or just your new version:

$ pytest -k api
$ pytest -k v1_1

UI Crud

In ui/crud, we support FlexMeasures’ in-built UI with Flask endpoints, which then talk to our internal API. The routes used there point to an API version. You should consider updating them to point to your new version.


In documentation/api start a new specification v1_1.rst with contents like this:

.. _v1_1:

Version 1.1


.. qrefflask::
  :blueprints: flexmeasures_api, flexmeasures_api_v1_1
  :order: path

API Details

.. autoflask::
  :blueprints: flexmeasures_api, flexmeasures_api_v1_1
  :order: path

If you are ready to publish the new specifications, enter your changes in documentation/api/change_log.rst and update the api toctree in documentation/index.rst to include the new version in the table of contents.

You’re not done. Several sections in the API documentation list endpoints as examples. If you want other developers to use your new API version, make sure those examples reference the latest endpoints. Remember that Sphinx autoflask likes to prefix the names of endpoints with the blueprint’s name, for example:

.. autoflask::
   :endpoints: flexmeasures_api_v1_1.post_meter_data