-bash: flutter: command not found

On Mac OS, insert single quotes OR double quotes around the file path like below. It's better to work like this with file paths in source files:

export PATH="/Users/carsoncarbery/development/tools/flutter/bin":$PATH

or

export PATH='/Users/carsoncarbery/development/tools/flutter/bin':$PATH

export PATH=/Users/carsoncarbery/development/tools/flutter/bin:$PATH