i18n question

[barren token]

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[bleak atlas]

The latter implies there is a file called commands.json which has keys pingName and pingDescription. You don't have that so it resolves to pingName which is invalid so through @sapphire/shapeshift validations that @discordjs/builders uses an error is thrown.

You should also have an understanding of the i18next API when using this plug-in: https://www.i18next.com/overview/getting-started

I really don't understand this question. Please provide examples. Also:

[flat valley]

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[bleak atlas]

What's the error it gives

[bleak atlas]

resolveKey's return type is string | null and content has to be string | undefined so yeah that error makes sense. Instead of casting it, you should write it as

(await resolveKey(...)) ?? undefined

though you should actually check if the resolved key gives a string value before even trying to send it.