Random testing represents a simple and tractable way for software assessment. This paper presents the Seed tool that can be used for the uniform random generation of recursive data structures such as labelled trees and logical formulas. We show how Seed can be used in several testing contexts, from model based testing to performance testing. Generated data structures are defined by grammar-like rules, given in an XML format, multiplying Seed possible applications. Seed is based on combinatorial techniques, and can generate uniformly at random k structures of size n with an efficient time complexity. Finally, Seed is available as a free Java application and a great effort has been made to make it easy-to-use.