He starts an automated test and gives the stream of summons his full attention, and gets one a moment later.
She finds the oil she's looking for and takes the lens out of her mouth. "Why do you have a computer?"
She doesn't have a rebuttal to that, but still seems to find it deeply strange. She mutters to herself as she assembles her various arcane objects. Finally, she smears the lens with a drop of oil and mutters further over it and then holds it over her eyes. "Right, tell a lie, see if this is working."
She winces. "And what's your story of what you're doing here?"
"Explain 'the usual way'."
"...I get a little note in the back of my head that says 'a summon you could answer', and I pull on it, usually not fast enough before another fairy gets it, and I appear in a circle and work out a deal and carry out the deal and get paid and then get unsummoned and go home. Would you mind explaining your definition of 'demon' since mine is only one species?"
"Maybe after the duration on this runs out. Summoned from where?"
A spark of green light flickers around the edge of her lens and she scowls and flicks it and quickly asks, "Under what circumstances are you likely to lie to me in the near future?"
"Is -" There's another flicker. She sighs and frowns at her lens and puts it in an empty plastic baggie from her bag. "Okay. You don't seem very good at explaining things from a starting point of 'what the hells are you talking about' so I'll do it and maybe that'll help. This is Earth. Humans live on it. So do a lot of mostly hostile supernatural sapients mostly from other dimensions collectively called 'demons', ranging from 'lethal nuisances with convenient allergies' through 'unkillable hellgods' and thousands more in between. If it talks and it's not a human or a parrot it's a demon. If it doesn't talk but it isn't too friendly with the laws of physics and wants to eat you and comes from not-Earth, it's a demon. With me so far?"
"So you would. And you are not recognizably a known not-universally-hostile species. So. The USADI is the United States instance of a government pseudomilitary body intended to handle demons - mostly vampires by the numbers; they're a sort of special case because they're parasitic on dead humans, memories and appearance and all, and very common. The USADI and equivalent foreign organizations sprang up when something called the 'Slayer line' was wiped out a few decades ago. Based on the reported supposed powers of the Slayers, which were 'be one teenage girl with super strength and speed and magically implanted martial arts knowledge and prophetic dreams', the USADI ought to be a million times more effective; in practice she had a kind of mythical aura to her and when the demons wiped out all the potential replacements and then the last Slayer all the demons everywhere went fucking nuts. Before that most people didn't even know they existed and now humans are generally on the defensive."
"Good for the Earth you know. I am a witch, but if the USADI finds out I'm a witch and that I'm any good at it they will insist that I join up with them right then. Which I may well wind up doing anyway but I want a better negotiating position than I can get right now and also it'll make my parents very upset. So I'm not thrilled with the prospect of hauling you to their office and explaining what just happened, but it seems like you might be extremely relevant to their extremely important projects."
"Yeah. Not a common thing, but it's not outside the bounds of magic."
"Sure, but they require materials I don't have on hand and we deal with potential apocalypses alternate Tuesdays."