Greece agreement does not guarantee a good deal – or permanent salvation

Developments in negotiations are an improvement on mutual hostility - but the glaring hole is likely to be the lack of detail on debt relief

There are three related rules of thumb to apply to Greek bailouts. First, remember agreement does not guarantee a good deal, let alone permanent salvation. Second, in assessing the above, ask whether it is really credible that Greece's debt-to-GDP ratio will fall to a sustainable level as a result of the plan. Third, bear in mind that financial markets' euphoria for Greek deals tends to last only about 48 hours.

All will be relevant in coming days, now that the action in Brussels is generating a whiff of optimism. Thursday is billed as the moment that six months of negotiations and standoffs will conclude with compromise and agreement.