It's now possible to build Skype tools into your own website, or other applications. Nobody officially knows this, of course, because, typically, Skype hasn't actually announced it - but if you download the latest build today, you'll spot the innovation in the install log.

What on earth is a Skype API? Skype is an instant messenger, but specially designed to allow non-expert users to talk to each other over the Internet. The trick is available with rival IM services like MSN, AOL and Yahoo! but many users find it hard to set up. Skype's install is comparatively idiot-proof. And the API means that programmers can add the Skype IM features to their own work.

No response has been forthcoming from anybody at Skype HQ, but a quick search of the Skype directory found a developer who was happy to confirm: "Yes, it's out. And it's a pig."

The Skype API allows you to build "presence" into a website - or any other application - and looks like a valuable tool for tech support. There's a beta-test site, to be unveiled in the next two weeks, where a conferencing system has been enhanced, so that the standard PHP threading doesn't just show who posted a message, but also shows whether they are online, and available for Skype chat. Click on the icon, and your request to chat - either via text or by voice - will be passed through the network.

Secretly, developers are rushing to prepare a friendlier set of tools. "There's a Canadian outfit, which I can't name yet, which is wrapping the API up in something that you don't have to be an expert C++ programmer to use," said our source. "I think they're doing a Java version, and a Web developer version."

Attempts to get more details were met with a stonewall NDA disclaimer, but it's clear from bulletin board chat that the system is well advanced, and being deployed by an initial beta test community. We found a well-populated set of debate threads on a hidden website, where issues were being discussed - but where the discussion can be taken online instantly if you have Skype enabled.

The same applies to blogs. The presence of the composer is signalled as soon as they set their Skype status to "online" or "SkypeMe" and if SkypeMe is picked, then anybody can start a voice conversation.

"It works pretty well, but the drawback is the interface to standard phone systems," said one tester. "The system works astonishingly well in the North American area, where Skype has a lot of PSTN gateways; but European users tend to complain a lot about having serious issues with voice quality."

Another test application being developed is a more comprehensive Skype phone book, where people can list their interests in more detail than in the basic Skype client. Again, the phone book has presence, showing whether it's worth trying to make contact - if the user is offline, the icon is greyed out.

"There are so many applications possible, it's insane," enthused one convert. "But they do have to improve the links to orthodox and alternative phone services. Skype is still far too much of a PC owner's toy, and it needs to reach people with ordinary phone systems. Getting the SIP phone community online would be a big first step."

The API is now there, and installable, but don't even try to use it, even if you are an expert C++ coder. The documentation required to let programmers crack it won't be released till early November, say insiders.

Meanwhile, if you google for "SkypeMe" you may just be able to track down one or two of the hidden websites where beta-testers are playing with the new tools.