Knobs beat sliders: making the Claude API something you can feel
Field Notes, 2026-06-09
Fluffy Parrot puts Claude API parameters on knobs and per-run tabs with cost and time, so tuning feels like using an instrument.
Fluffy Parrot is a control surface for the Claude API: every parameter visible, tunable, and easy to compare across runs. The lesson that stuck from shipping it had less to do with the API than with how the interface changed how I used the tool.
Calling the API in code gets you answers, but not much sense of where you are in the parameter space. I wanted a surface where you could see and feel every parameter the API exposes, so building that intuition was part of the work.
The first version was a custom UI with sliders, buttons and knobs for those parameters. Precise, sensible, and a good start. Reading a value off a slider, though, is still close to reading it out of code.
The fix was physical, not technical
So I made the controls feel physical: hardware-style knobs in a VST-inspired interface. Same values, same ranges, but tuning suddenly felt tactile. You were turning something, not editing a line of code. That one change altered how I used my own tool.
When a task is about building intuition, the interface should make the variable space feel like a place you can move around in, not a config file you edit.
What made it an instrument
Giving every run its own tab, with its cost and round-trip time attached, so two takes sit side by side. Once you can read the diff, you stop trusting your memory. That is the moment a playground becomes an instrument.
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