Input to MediaWiki should be NFC-normalised UTF-8. MediaWiki may attempt to convert other input, but this may cause some operations (such as [[Special:ApiHelp/edit|edits]] with MD5 checks) to fail.
Parameters that take multiple values are normally submitted with the values separated using the pipe character, e.g. <kbd>param=value1|value2</kbd> or <kbd>param=value1%7Cvalue2</kbd>. If a value must contain the pipe character, use U+001F (Unit Separator) as the separator ''and'' prefix the value with U+001F, e.g. <kbd>param=%1Fvalue1%1Fvalue2</kbd>.
Some parameter types in API requests need further explanation:
MediaWiki:Api-help-datatypes-top/en-gb
