head to head
Agar.io asks more than Codenames, and the gap is execution.

Reads · Competitive PvP
A browser arena where your cell eats smaller players and flees bigger ones.

Reads · Pure Mind Games
A team word game about predicting how partners will read your clues.
Agar.io leans Reads (Competitive PvP); Codenames leans Reads (Pure Mind Games).
Agar.io leans clearly harder on execution.
Agar.io
Mouse steering and split timing
Codenames
No physical skill in giving word clues
Codenames leans a little harder on reads, though the gap is small.
Agar.io
Baiting and predicting human blobs decides fights
Codenames
Modeling how teammates interpret your clues is the game
Agar.io leans a little harder on variance, though the gap is small.
Agar.io
Spawn locations and lobby makeup random
Codenames
The fixed board adds little randomness mid-game
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Agar.io
Split-merge math is shallow but real
Codenames
Some clue-efficiency math underlies the prediction
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.