Notes:

Characteristics of a Game Agent or Intelligent Game Agent:

1. must provide an entertaining and engaging experience to the player

2. must act intelligently (clever or smart); but should not be highly intelligent
If it is highly intelligent then the entire time game agent wins.
If all the time game agent wins; then why would any player like to play that game?

3. must have planned and observable weakness(es) but should be difficult to defeat
If there are easy observable weakness(es) then the entire time player wins.
If all the time player wins; then how do you add an engaging factor in the game?

4. must be configurable by game designers or players
Game designers should be able to enable or disable the features of game agent(s).
i.e. Just by enabling and disabling features; they should be able to configure the intelligence level of a game agents from an easy to difficult. It should be possible to convert a difficult game agent to medium or easy game agent just by disabling some features. It should be possible to convert an easy game agent to medium or difficult game agent just by enabling some features of the game agent.

Players should be able to decide which game agent against he/ she would like to play
i.e. some players may would like to play against an easy game agent; some hardcore players may would like to play against a difficult game agent directly instead of a medium or an easy level game agent.

5. must perform within the CPU and memory constraints of the targeted platform
Especially in low end devices we find less memory and less processor;
so we need to focus on the targeted platform CPU and memory constraints.
Game agents should not add any delay in the game play experience at any time.

6. must learn and improve over time
If possible game agents should be able to learn and evolve by themselves over time.

7. must be appealing with respect to type of a game
The agents in the game world should have consistent look and feel according the type of game.
As stated the graphics of game agents should be appealing, with respect to game.
If you are building a horror game, then the game agents visual should bring the fear or horror feel, If you are building a game for fun, then the game agents visual should bring that fun or entertainment feel etc. Should follow graphics design principles.