可以使用Backlog API来查询要搜索的字段。具体方法为：

1.先获取需要查询的项目的ID：

curl https://{spaceKey}.backlog.com/api/v2/projects?apiKey={apiKey}

2.通过获取到的项目ID来查询搜索的字段列表：

curl https://{spaceKey}.backlog.com/api/v2/projects/{projectId}/searchableFields?apiKey={apiKey}

例如，查询项目ID为1的项目中可搜索的字段列表：

curl https://example.backlog.com/api/v2/projects/1/searchableFields?apiKey=API_KEY

返回结果如下：

{ "issue": { "id": 8270614568, "projectId": 1, "name": "Issue", "key": "ISSUE", "searchableCustomFields": [ { "fieldTypeId": 5, "id": 8325222246, "name": "Custom Field 1", "description": "", "typeId": 9, "required": false }, { "fieldTypeId": 6, "id": 8325222247, "name": "Custom Field 2", "description": "", "typeId": 9, "required": false } ] }, "wiki": { "id": 8316999441, "projectId": 1, "name": "Wiki", "key": "WIKI", "searchableCustomFields": [] } }

从结果中可以看出，项目中有两个可搜索的自定义字段，分别是"Custom Field 1"和"Custom Field 2"。