What is the difference between the effort parameter and response verbosity in Claude Opus 5?

The effort parameter controls how much Claude Opus 5 thinks, and by extension how deep its reasoning, tool calls, and argument construction go - it's fundamentally about internal computational work, not the length of the final visible answer.

Response verbosity, the actual length of what the user sees, is a separate concern that effort doesn't reliably control - lowering effort to save cost will not dependably make the visible response shorter, which surprises teams expecting effort to double as a length dial the way it might seem to on the surface.

To actually control response length, Anthropic's guidance recommends an explicit instruction in the prompt itself, such as asking for focused, concise answers with minimal caveats, rather than relying on the effort parameter to do that job.

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