A helper class so_5::rt::agent_context_t (aka so_5::rt::agent_t::context_t) was introduced in v.5.5.4 (see so-5.5.4: Another constructor for agent_t with context_t argument for details). Since then it is broadly used. Moreover the usage of context_t in agent's constructor is a recommended way for defining agent's constructors.

But until v.5.5.8 context_t could be used only for ordinary agents. There was no a possibility to specify and tune context_t for ad-hoc agents. In v.5.5.8 a new method so_5::rt::agent_coop_t::make_agent_context() was added. It allows to create and tune contexts for ad-hod agents:

so_5::rt::agent_coop_t & coop = ...;
auto a = coop.define_agent( coop.make_agent_context() // Default context
  // Add message limit.
  + so_5::rt::limit_then_drop< request >( 10 )
  // Add priority.
  + so_5::prio::p7 ); // Resulting context will be passed to the constructor of underlying agent object.