Something like:
"Company X is providing Wood Species, Grade, for the Client Name Project. This material is fresh sawn (reclaimed, RF Dried, etc.) and will (tune your response here based on material) have a variable moisture content high enough to cause further twisting, shrinking, and checking. Structural capacity of the timber will not be compromised and joinery design and member sizes have been engineered to account for this movement."
Or something like that. I'm not a lawyer... so you might best get your contracts reviewed by a local.
Note that you might want to include your warranty conditions / disclaimers. I work with one shop that will not warranty fresh sawn oak...
-Mike