Update: There seems to be some controversy here as to whether or not there really is a difference between vouching and guaranteeing, which impacts how it is translated. Please see the discussion I started on English L&U about this, where I believe the answers are supporting the idea that there is a difference, and explain what that difference is.
Japanese does not seem to have a readily available equivalent for the concept of "vouching" for someone when you are introducing someone for work, or as a possible date, or whenever there is some kind of favour involved and it's not just social.
To be more accurate, in Japanese culture, when one introduces someone else, the default assumption is that you are vouching for that person.
Which means that just about any and every introduction comes with a fair amount of responsibility. Which might be fine, except Japanese tend to err on the side of caution by being hesitant to make introductions, for whatever purpose, for fear that something might go wrong.
The words the dictionary provides for "vouch" is
請け合う【うけあう】, both of which mean "guarantee", which is much too strong. I think because the default assumption is that any introduction comes with a sense of vouching for that person, to then add words only stresses the assurance, not qualify it.
The problem with anything like "guaranteeing", is that it implies that if something goes wrong, you can come back to me, either for compensation, or maybe just to punch me in the stomach, or something.
In English language and culture, when I'm vouching for someone, I am telling you about the content of their character. What transpires from their actions is between you and them. Guaranteeing is about putting assurance on future actions and transactions.
So is there a way in Japanese I can say I'm vouching for the person without guaranteeing their future actions?
Also, can I qualify a meeting by saying I'm not vouching for someone? In other words, despite the fact that this introduction is to help you with something, I'm only making the introduction because I'm trying to help, but I don't know the person I'm introducing well enough to give you any assurance.
This is somewhat a cultural issue as well as a language issue, which means I wouldn't expect there's some perfect term that I simply haven't discovered yet. If this is a concept that has to be described in some way so as to introduce it to the language, then let's concoct something new.