na-adjective, noun
Describes something that is practically useful and makes life easier. Often used for tools, gadgets, or small items that serve multiple purposes.
See also: 重宝
このアプリはとても調法だ。
This app is very handy.
調法な道具を一つ持っていると便利だ。
It's convenient to have one useful tool.
便利 is the most common word for 'convenient' and is used broadly. 調法 implies a more personal, practical usefulness, often for specific items or situations.
役に立つ is a verb phrase meaning 'to be useful' and can be used in more formal or general contexts. 調法 is an adjective-like noun and feels slightly more colloquial and concrete.
The exact derivation is uncertain. The spelling 調法 suggests 'arranging methods,' while 重宝 suggests 'treasured thing,' both fitting the meaning of something convenient and useful.