This is the 4963rd most frequent Spanish word.
eficaces
Effective; capable of producing the desired result.
Here, 'eficaces' is used as a plural adjective describing 'herramientas', indicating they are effective in achieving their intended purpose.
Estas herramientas son muy eficaces para resolver problemas complejos.
These tools are very effective in solving complex problems.
In this sentence, 'eficaces' describes 'tratamientos', showing that they yielded positive results in practice.
Los tratamientos sugeridos por el doctor resultaron ser eficaces.
The treatments suggested by the doctor proved to be effective.
Here, 'eficaces' modifies 'métodos', expressing an ongoing search for methods that are efficient in fulfilling the goal.