CodinGame doesn't have an official API yet.
Use CodinGame unnofficial community services at your own risk.
Useful Community Tools
Puzzle Search by eulerscheZahl
You can look for puzzles using the search bar in the CodinGame header. However, it does only search for keywords in the puzzle titles.
eulerscheZahl has made a more complete search tool:
List of Puzzles by Stilgart
This tool provides the list of all puzzles in the training section, with their charateristics and some statistics. You can check which are the most attempted/solved puzzles and sort them by community ratings or success rate.
Brutaltester by Magus
This tool allows you to simulate the CodinGame arena of bot programming games and test different versions of your AI against each other.
CG Points Details by Royale
Learn how many points you can get in multiplayer games. It can help to prioritize which games to start.
CG Multi by Azkellas
To complete the previous tool by Royale, CG Multi allows you to check your bot programming rankings at a glance. It also provides some statistics of submissions in bot programming games.
CG Stats by Magus
CG stats provides you with statistics of your latest submission in a multiplayer game.
Additional tools and ressources can be found in this list created by BlaiseEbuth.