Six Reasons AI Models Ignore Your MCP Tool — and How to Fix Each One

An analysis of 4,749 public MCP servers reveals six common reasons why registered tools are overlooked or bypassed by AI models. The most frequent issues include indistinct tool descriptions that fail to differentiate similar tools, and missing parameter descriptions that leave models unable to determine what values to supply. Generic or synonymous tool names — such as get_thing versus fetch_thing — also cause models to guess incorrectly, while oversized tool lists can overwhelm the context window and dilute model attention. Additional culprits include case-sensitivity mismatches that make a tool appear broken after a single failed call, prompting the model to abandon it entirely. The findings suggest that small, precise changes to naming, descriptions, and schema definitions can significantly improve how reliably AI models select and use the correct tool.