[TYPO3-english] External Import and JSON

[Jeppe Donslund]

I want to use the extension externalimport to import external data into my TYPO3.
I insert the path to an php file in the TCA as desrbed in the documentation. Taht php file returns valid JSON.
But I get this error: Data could not be fetched (connector error: No JSON data has been defined.)

Should the link end on ".json" or is it something else that is wrong?