How would he know it's a crisis if you didn't give context? I think his response is appropriate considering you hadn't said why you needed to see him. Even if his texting guidelines are restricted to scheduling, it would make sense to say--I'm in crisis. Do you have an appointment today?

Of course, crisis has become a vague and overused term, so unless he knows what a crisis is to you, it might be important to write a brief explanation, like: I lost my job and am spiraling fast, can you see me today?

Sometimes, when it's not a crisis, but I'm just having trouble coping, I'll say something like, "I'm really struggling and couldn't go to work. It's not a crisis, but I could use support to keep from getting worse. Do you have an opening today?