Writing tenders is not as easy as it seems, managing them effectively even less so. Many years working in the 3PL sector exposed us to the good the indifferent and the poorest tenders.
If you want to get the best from your suppliers, you must be prepared to trust them. You must give them all the information they need to respond adequately. Failure to do so will result in conservative costs (translate to higher) or so many caveats that render the submissions impractical. Deal with sensitivities with appropriate confidentiality clauses - that are workable and enforceable.
In addition, information must be presented clearly and concisely; do not leave anything open to interpretation, unless ambiguity will improve the originality of result and not the quality. We make a point of conducting all necessary data cleansing and analysis prior to release with the tender. This is not holding the hand of the respondent, it improves confidence in the voracity of the submissions and saves considerable time sense checking submissions post deadline.