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I'm interested in the kind of case you have in mind. But, whatever it is, I'm pretty sure the answer is no. The only way for the user to invoke a native skill is to trigger it with a voice command. 3rd party skills have no access, of any sort, to native skills (or, of course, other 3rd party skills.) For example, if you built an "addition" skill, and the user requested subtraction, there's no way to pass the subtraction request on the Alexa's built in math skill. Steve

tl;dr - Depending on what sort of request you're making, and how close it is to your existing utterances, you may not need to do anything. It's interesting to me that you [i]want[/i] this behavior, as it sounds like something Alexa does that has been frustrating for me. While there's no way that you can configure Alexa to "take my utterance, strip out the trigger word, and pass the rest back to the built-in skills", it's worth noting that Alexa is already using the entire utterance context to determine whether to trigger YOUR skill or to pick built-in functionality. This is especially likely to happen when you have a trigger word that is not an English word. For example: Lets assume that you have a skill that gives you star wars information, and it's named "Holocron" (which is the word for a data store in the star wars universe). This isn't an English word, so Alexa will never independently match that. However, given context, it can figure out that your audio was supposed to match that skillname that isn't a known word. So, if you ask it "Ask Holocron what a star destroyer is", Alexa will hear it as something like "ask {hall a crayon?|all a crone?|Holocron} what a star destroyer is", and not know what that first bit of the question was. When it sees the rest of the utterance, though, assuming it matches the "what is a star destroyer" utterance you set up for your Holocron skill, it will obviously be able to disambiguate between the three choices, and properly select the Holocron skill. However, if you ask it something that doesn't obviously tie it back to your skill, it has a much harder time. If you wanted to understand how to use the skill, and you said "Ask Holocron for help", Alexa might have a really hard time tying that back to your original skill, since "for help" is a super generic term not specific to your set of utterances. Instead, Alexa may choose to go with "ask all a crone for help", and since that isn't a skillname, it would default back to built-in behavior, which will almost certainly result in the frustrating "I couldn't find an answer to your question" response. Anyhow, this likely doesn't help with your use case, but I figured I'd give you an overview of what I've anecdotally/experimentally seen to be the way Alexa deals with ambiguity, since maybe that can help inform your design.

It can't and, personally, I don't expect it is a feature that Amazon will implement. Yes, from a usability standpoint, that would be a handy thing for both users and developers. From from a legal standpoint, I think Amazon consider it important to distinguish when you are interacting with a built in feature they are liable for, and a 3rd party feature someone else is liable for. For example, the Ask My Buddy skill is (in my non-legal-expert opinion) a lawsuit waiting to happen. If someone uses this skill to grief someone and it goes to court, Amazon is a big target because they have lots more money than the nobody who came up with the skill. However, the clearly the distinction is between Amazon provided services and 3rd party services, the easier it is for Amazon to mount a defense in lawsuits of this nature. It isn't always about the tech. :-(