Cook the edamame beans in boiling water or over steaming water.
Meanwhile, cut the cucumber in half vertically, scoop out the soft flesh, then cut it into half moon shapes. Slice the spring onions and cut the tomatoes in half.
Drain the beans and rinse with cold water. Put them in a mixing bowl and add the vinegar, agave, olive oil, lemon juice and salt an pepper. Carefully fold in the other veggies.
Scatter the rocket leaves in a serving bowl or platter. Arrange the marinated veggies on top, then pour over any remaining dressing.
Toss, just before serving.