Thanks for quick reply.
I tried the following and it still return all the field
rbt api-get
http://reviewboard.com/api/review-requests/110/?onlyfield=status{"stat": "ok", "review_request": {"status": "pending", "last_updated": "2015-10-28T21:51:08Z", "target_people": [{"href": "
http://reviewboard.com/api/users/gang/", "method": "GET", "title": "gang"}], "depends_on": [], "description_text_type": "markdown", "testing_done_text_type": "markdown", "ship_it_count": 1, "close_description_text_type": "plain", "id": 110, "links": {"diffs": {"href": "
http://reviewboard.com/api/review-requests/110/diffs/", "method": "GET"}, "repository": {"href": "
http://reviewboard.com/api/repositories/1/", "method": "GET", "title": "engn"}, "changes": {"href": "
http://reviewboard.com/api/review-requests/110/changes/", "method": "GET"}, "self": {"href": "
http://reviewboard.com/api/review-requests/110/", "method": "GET"}, "update": {"href": "
http://reviewboard.com/api/review-requests/110/", "method": "PUT"}, "last_update": {"href": "
http://reviewboard.com/api/review-requests/110/last-update/", "method": "GET"}, "reviews": {"href": "
http://reviewboard.com/api/review-requests/110/reviews/", "method": "GET"}, "draft": {"href": "
http://reviewboard.com/api/review-requests/110/draft/", "method": "GET"}, "file_attachments": {"href": "
http://reviewboard.com/api/review-requests/110/file-attachments/", "method": "GET"}, "submitter": {"href": "
http://reviewboard.com/api/users/sam/", "method": "GET", "title": "sam"}, "delete": {"href": "
http://reviewboard.com/api/review-requests/110/", "method": "DELETE"}, "screenshots": {"href": "
http://reviewboard.com/api/review-requests/110/screenshots/", "method": "GET"}, "diff_context": {"href": "
http://reviewboard.com/api/review-requests/110/diff-context/", "method": "GET"}}, "changenum": null, "bugs_closed": [], "testing_done": "none", "close_description": null, "text_type": null, "time_added": "2015-10-28T21:49:37Z", "extra_data": {"calculated_trophies": true}, "public": true, "commit_id": null, "blocks": [], "description": "demo3", "issue_resolved_count": 0, "issue_open_count": 0, "branch": "temp_mojgans_db2_main_rbtool", "approved": true, "url": "/r/110/", "absolute_url": "
http://reviewboard.com/r/110/", "target_groups": [], "summary": "demo3", "issue_dropped_count": 0, "approval_failure": null}}