Does anyone have an immunity agreement template they would be willing to share?

Also, when offering a co-defendant a reduced sentence to testify against the primary defendant, should I keep the agreement oral or place it in writing? If it should be in writing, does anyone have a template for that?

I thank you all in advance.

Justin
cunnijt@co.ector.tx.us

The offer to the co-defendant will be admissible when the co-defendant testifies, so why not put it in writing to avoid any misunderstanding as to what the offer is? "In exchange for truthful testimony by ___________, the State agrees to offer________."