How to spawn custom tool when specific block is broken

We have created a new custom sword (tool): https://imgur.com/quBfhAV

We also created a custom procedure for doing the spawn when a grass block is broken (we are starting very simple to start learning): https://imgur.com/OD3qJBb

However, our custom sword is not available to select as the "Spawn entity": https://imgur.com/Ng6F02r

Any ideas on how to accomplish this would be great, thanks!