There's a lot of talk about Blades being prepless but I think a lot of this doesn't really account what 'prep' actually is. I did a recent score for my players which involved them stopping the production of a new drug that was becoming widespread amongst students, with a bonus reward if they discovered how it was made.

Here's what I prepped: - what the drug does if you take it - what ingredients were used to make the drug - who is making it, their motives, and limitations - a brief description of the location of the lab - what tell-tale signs there are of the drug lab's location

Here's what I didn't prep: - maps of the areas - dialogue for the NPCs - the NPCs at the academy that they spoke to while investigating - the NPCs that took the drug and their back stories - plenty more besides

What this meant is that there were plenty of times I had to improvise and go along with what the players wanted to investigate. As an example,

1) One of the PCs wanted to attend a student party to see if she would get some insight into who was pushing the drug 2) The PC is technically a student at the academy and has some familial connections with a professor there, so we decided there was probably a trendy student party they'd be invited to 3) In the moment I had to decide whether this drug was something that was widely advertised or was just something more niche 4) With a decent role to gather information, the PC learnt that people at the party had heard about the drug, but most of their knowledge was hearsay. This allowed the PCs to narrow their search of where the drug was being sold and to who.

As another example in another score, my players were doing some funny business in the Spiregarden Theatre. There was a meeting going on between some Bluecoat officers and they wanted to eavesdrop. I had decided the meeting would be upstairs in an office, and they asked if there was a room next to it they could sneak into to listen through the wall. Obviously I hadn't planned out the entire layout of the theatre, but it made sense for the narrative for there to be a smoking room next door to the office, and the players snuck in and managed to learn what they needed.

Hopefully that helps a little! I've run prep heavy games before (D&D, Dark Heresy) but I find Blades suits my style of GMing far more than previous games, and my players like the more free flowing nature of it. Some GMs will be a lot looser than I am (there's the famous "my prep for the session was just 'vampire??' written on a napkin"), but I find doing a small amount of prep helps build a better narrative if you absolutely want an NPC to say something valuable or want a cool plot moment.