-- Database schema
| cites : cited_paper_id [ TEXT ] , citing_paper_id [ TEXT ] | paper : paper_id [ TEXT ] primary_key , class_label [ TEXT ] | content : paper_id [ TEXT ] content.paper_id = paper.paper_id , word_cited_id [ TEXT ] |
-- -- Calculate the percentage of words used in Agents class label.

SELECT CAST(COUNT(DISTINCT CASE WHEN T1.class_label = 'Agents' THEN T2.word_cited_id ELSE NULL END) AS REAL) * 100 / COUNT(DISTINCT T2.word_cited_id) FROM paper AS T1 INNER JOIN content AS T2 ON T1.paper_id = T2.paper_id;