"Sweet, easy enough, I'll just use X, Y and Z, no problem."
"Oh but sorry you have to use A, B, and C instead. Oh and it'll need to connect to D for reporting, and we'd like it to sync with E which we've never done but they have an API so it can't be too hard, right? Oh and it needs to fit this design we've already approved that's about as far from native to the platform you're developing for as it could be and has a ton of UX issues that require fundamental changes to fix, which you'll uncover as you work. That's about as easy, right?"
"...."
[EDIT] oh and also one "minor" feature we're going to toss in later is actually big enough to build an entire company around so you'll have to waste a bunch of time talking us down from that while we quietly lower our opinion of you, and we've accidentally described a few things which are basically impossible by egregiously violating e.g. CAP theorem or being what's effectively a highly-available distributed filesystem that needs to fit without our timeframe and budget, which is 1/20 what it would take to maybe build that and that alone.
"We want you to do this."
"Sweet, easy enough, I'll just use X, Y and Z, no problem."
"Oh but sorry you have to use A, B, and C instead. Oh and it'll need to connect to D for reporting, and we'd like it to sync with E which we've never done but they have an API so it can't be too hard, right? Oh and it needs to fit this design we've already approved that's about as far from native to the platform you're developing for as it could be and has a ton of UX issues that require fundamental changes to fix, which you'll uncover as you work. That's about as easy, right?"
"...."
[EDIT] oh and also one "minor" feature we're going to toss in later is actually big enough to build an entire company around so you'll have to waste a bunch of time talking us down from that while we quietly lower our opinion of you, and we've accidentally described a few things which are basically impossible by egregiously violating e.g. CAP theorem or being what's effectively a highly-available distributed filesystem that needs to fit without our timeframe and budget, which is 1/20 what it would take to maybe build that and that alone.