The answer depends entirely on his prior criminal record. Trespassing is a class 3 misdemeanor (at least in the way you described the situation) and the larceny is most likely a class 1 misdemeanor (as long as the collective value of the tools does not exceed $1k and all belong to the same victim). If they are all misdemeanor charges, the most he can get is two sentences of 120 days (two larceny counts run consecutively). Get a lawyer and talk to him about the situation. The information you gave seems to be in your boyfriends favor. For example, if you stole 7 tools from one person in one transaction, that would only be one larceny.
The information provided by Attorney Matthew V. Silva is based upon the generic and ambiguous facts presented in short questions. Without a full consultation with an attorney, you should not rely upon any information presented in this forum. The intricate facts of every case are different. The information provided is not legal advice and should not be the basis of any decision without the actual guidance of an attorney. Further, any information provided by Attorney Matthew V. Silva should not be perceived as a willingness to represent you or actual representation. If you would like to speak with Attorney Matthew V. Silva, please call Silva and Sweet, PLLC at 910-333-9833 or visit www.silvaandsweet.com.
I agree with the other responses that he needs to consult an attorney ASAP. Just because he was arrested does not mean he violated his probation, and under those facts he should plead not guilty in court. My office is in Concord if you would like to make an appointment, and we offer free consultations. Good luck.