Utility code to get the keys from a document in a specified MongoDB database and collection.

mongoGetKeys.py

#!/usr/local/bin/python

import sys
from pymongo import MongoClient

if len(sys.argv) < 3:
    print 'usage is: ' + sys.argv[0] + ' databaseName collectionName'
    sys.exit()

dbName = sys.argv[1]
collectionName = sys.argv[2]

print 'Database: ' + dbName + ' Collection: ' + collectionName

connection_string = "mongodb://localhost"
connection = MongoClient(connection_string, safe=True)
db = connection[dbName]
collection = db[collectionName]
document = collection.find_one()
if document is not None:
    print 'document keys: '
    print document.keys()
else:
    print '*** No Document Found ***'

connection.disconnect()

Note that this only gets the top level keys -- it doesn't delve into subdocuments.
On the command line give the utility the name of the database and the collection name you want examined.