Child labour:

In 2001, a voluntary agreement called the Harkin-Engel Protocol, was accepted by the international cocoa and chocolate industry to eliminate the worst forms of child labour, as defined by ILO's Convention 182, in West Africa. This agreement created a foundation named International Cocoa Initiative in 2002. The foundation claims it has, as of 2011, active programs in 290 cocoa growing communities in Côte d'Ivoire and Ghana, reaching a total population of 689,000 people to help eliminate the worst forms of child labour in cocoa industry. Other organisations claim progress has been made, but the protocol's 2005 deadlines have not yet been met.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What type of agreement was the 2001 Harkin-Engel Protocol?
voluntary