You needn't necessarily spill the whole list of Things What Mustn't be Done and Conditions, depending on the depth (or lack thereof) in the relationship, but a simple "I have some health issues; I know my limits and I'll let you know about them if I suspect they are going to come up or if something happens; in case of emergency, I have a card with information in my bag/pants pocket/with the person at the other end of that leash" is unlikely to be out of order. 99 times out of 100, 999 times out of 1000, that card may not be necessary. That 100th or 1000th time, depending on the situation, it could save your life by giving someone the right knowledge to assist you properly, or at least keep them from panicking and seeing that you get proper care.
In other generally related news, with the help of IRC I thought of a niche service that may well be going unfilled: housecall dominants for people with disabilities. Disability may be affecting a person's ability to go out and look for an appropriate partner, if they are not lucky enough to have one at home; people with disabilities need appropriate-to-them caring-for too. A dominant service that specializes in creative work to avoid causing assorted forms of failure and badness, and with side education in medical care to back that up (not only would the dom know kink, but know how a given disability is likely to affect a person straight out of the box, and how to learn each person's situation's quirks quickly), might actually be a really good thing for someone. (And why should homebound submissives and switches be the ones to get all the fun from this service? Why should not a homebound dominant have the enjoyment of ordering around a submissive who is also trained in personal care?) And apparently some correctly applied play is good for some sorts of chronic pain.
It's vaporware, but since it could be useful, I'm sending it off into the aether where it might actually be picked up by someone who could do something with it, make it happen, provide a useful service to people who could really use a little more fun. ;)