Eager, avid, keen, anxious, agog, athirst mean actuated by a strong and urgent desire or interest.
Eager implies ardor and, often, enthusiasm; it frequently also connotes impatience.
Avid adds to eager the implication of greed or of unbounded desire.
Keen suggests intensity of interest and quick responsiveness in action.
Anxious emphasizes fear lest one’s desires be frustrated or one’s hopes not realized; it often additionally connotes insistence or perseverance in making one’s desires known.
Agog suggests being caught up in the excitement and bustle attending something interesting about to be begun or an event eagerly awaited.
Athirst implies yearning or longing more vividly than the others; it seldom connotes readiness for action.