It consists of:
Reaction note (blog entry)
1. An introductory paragraph identifies the main argument / points of the source. This part should be no longer than 50-100 words. Be selective. You do not have space to write a summary of the source; and
2. Assessment of the source identifies both its strengths – contributions to the topic discussed – and its weaknesses in discussing it.
Support each point by a short argument (reason) or reference to evidence. It is better to raise fewer points and support them well, than to just mention more points.
Write clearly and professionally. Keep your audience (as described above) in mind. Assume that the audience id familiar with the topic, although not with the source. There is no need to define concepts (unless a concept is a point in your evaluation).
You do not have space to write a conclusion.