# Setup a PoC

**URL:** <https://hub.mender.io/t/setup-a-poc/7393>\
**Category:** General Discussions\
**Created:** [December 16, 2024, 3:21am UTC](https://hub.mender.io/t/setup-a-poc/7393 "2024-12-16T03:21:47Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![Tom-Isaacson](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/tom-isaacson/32/2371_2.png) [@Tom-Isaacson](https://hub.mender.io/u/Tom-Isaacson)\
**Post date:** [December 16, 2024, 9:26pm UTC](https://hub.mender.io/t/setup-a-poc/7393/4 "2024-12-16T21:26:16Z")

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Ok, documentation is a bit poor. `X-MEN-Signature` is actually a signature as explained in [How to write a custom client interfacing a Mender server](https://hub.mender.io/t/how-to-write-a-custom-client-interfacing-a-mender-server/1353). Documentation could do with an update.

My confusion now comes from all the different APIs being able to send custom data. That article says we need to call [Device inventory](https://docs.mender.io/api/?shell#device-api-device-inventory) with a minimum of `device_type` and the `artifact_name`. But this isn’t mentioned in the API spec? Then we can call [Deployments v2](https://docs.mender.io/api/?shell#device-api-deployments-v2) but this also includes `additionalProperties`. If I just add `additionalProperties` here I get 204 No Content so I assume I need to declare all additional properties in the inventory. But if this is the case why do I have the ability to add them to the Check Update call? Is this in case the values change?

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_[View the full topic](https://hub.mender.io/t/setup-a-poc/7393)._