Adsorption energy is a key reactivity descriptor in catalysis, enabling the efficient screening of potential catalysts. However, determining adsorption energy involves comparing the energies of multiple adsorbate-catalyst configurations, which is computationally demanding due to a large number of possible configurations. Current algorithmic approaches typically enumerate adsorption sites and configurations without leveraging theoretical insights to guide the initial setup. In this work, we present Adsorb-Agent, a Large Language Model (LLM) agent designed to efficiently derive system-specific stable adsorption configurations with minimal human intervention. Adsorb-Agent leverages built-in knowledge and emergent reasoning capabilities, significantly reducing the number of initial configurations required while improving accuracy in predicting the minimum adsorption energy. We demonstrate its performance using two example systems, NNH-CuPd3 (111) and NNH-Mo3Pd (111), for the Nitrogen Reduction Reaction (NRR), a sustainable alternative to the Haber-Bosch process. Adsorb-Agent outperforms conventional "heuristic" and "random" algorithms by identifying lower-energy configurations with fewer initial setups, reducing computational costs while enhancing accuracy. This highlights its potential to accelerate catalyst discovery.