Embodied Conversational Agents (ECAs) are becoming more widely used for various applications, notably in health. Some studies have demonstrated the effectiveness of delivering Motivational Interviews (MIs), a patient-centred behaviour change method, with ECAs. Despite showing promise, the effect of agent communication style on MI effectiveness remains underexplored. Directness has been shown to impact satisfaction and preference of dialogue systems, and effectiveness in some cases. However, outside of verbal style, how to control directness in ECAs to achieve these goals is not well understood. We designed an ECA to convey different levels of directness through language and Non-Verbal behaviours (NVBs), then evaluated the impact of language and NVB on directness with a perception study. The results showed that language influenced perceived directness, and that NVB contributed when aligned with indirect language. These findings suggest ways to shape conversational agents' communication style to enhance their effectiveness.