We describe about dynamic discovery and coordination of agent-based semantic Web services. Matchmaking and brokering are multiagent coordination mechanisms for Web services. Both have performance trade-offs, but the Web Ontology Language for Semantic Web Services (OWL-S) can handle extensions that address some of the shortcomings. We focus on the broker, analyzing both its interaction protocol and reasoning tasks. We also describe OWL-S's exec extensions, detail their implementation's basic features, and explain how these features address the broker's reasoning problems.