Vision agents are the default for operating web apps that don't expose APIs. Most teams default to vision agents because the alternative, writing an MCP or REST surface, is too expensive to build. The cost of the vision approach is treated as a fixed price. Current vision agents require detailed prompts to succeed in tasks, and they are still prone to making mistakes. Better vision models reduce error rates, but they do not reduce the number of screenshots required to reach the relevant data, each of which is worth thousands of input tokens.