This thesis describes the implementation and evaluation of an extension to the agent control language IndiGolog that uses the ES logic as description language, which allows a higher expressiveness including nested belief operators, quantifying-in and arbitrary first order logic sentences as the objective knowledge base. To exploit the full expression power of ES, a first-order logic theorem prover is used to evaluate requests against the agents knowledge base. For those changes the modular build-up of IndiGolog is harnessed, such that only a redevelopment of the evaluator was needed, whereas the remaining system was unchanged. After an introduction into the ES-logic and the IndiGolog platform the construction of the new evaluation module is described. Afterwards the new system is evaluated against original IndiGolog and Flux, another agent framework, and the advantages in terms of expression power are lined out.