Paper on Agent Interfaces to the Web accepted at the Web Conference 2026
Abstract:
LLM-based agents are increasingly used to automate web tasks such as product search, offer comparison, and order placement. Current research explores different interfaces through which these agents interact with websites, including traditional HTML browsing, retrieval-augmented generation (RAG) over pre-crawled content, communication via Web APIs using the Model Context Protocol (MCP), and natural-language querying through the NLWeb interface. Yet no systematic comparison of the effectiveness and efficiency of these interfaces on identical challenging task sets exists. To address this gap, we introduce a testbed consisting of four simulated e-shops, each offering its products via HTML, MCP, and NLWeb interfaces. For each interface (HTML, RAG, MCP, and NLWeb), we develop specialized agents that perform the same sets of tasks, ranging from simple product searches and price comparisons to complex queries for complementary or substitute products and checkout processes. We evaluate the agents using GPT-5 and GPT-5-mini. Our evaluation shows that RAG, MCP, and NLWeb agents outperform HTML browsing agents by 11 percentage points in task completion while requiring 2–5 times fewer tokens on search-oriented tasks. The GPT-5 RAG agent achieves the highest task completion rate (0.79) while maintaining moderate token consumption.
Preprint version of the paper:
Project website:
Conference website: