What exactly is a Flurry of Blows?

Question

What part of attacks a monk makes during a full-attack routine constitutes a Flurry of Blows class-feature?

I was recently pointed out, Flurry of Blows says:

A monk must use a full attack action to strike with a flurry of blows.

This means, it isn't necessary the whole full-attack, but maybe only some part of it. Should I elaborate, I always played monks with Flurry of Blows being the whole full-attack? Now, after some digging I see three possible cases, and I'm not sure which one is correct:

1. I was right, and Flurry of Blows is a full-attack with some bonus attacks described by class-feature itself, as well as any other potential bonus attacks which all should qualify for Flurry of Blows restrictions.
   As a 'backup' for this version there is a table of a monk class calling attack bonuses of all attacks a monk makes using Flurry of Blows "Flurry of Blows Attack Bonus". Not "Attack Bonus When Using Flurry of Blows" or something similar. I think you got a point. Another 'proof' is a Fist of the Forest example statblock, which excludes bite attack from the whole routine (because it isn't an unarmed strike or a monk weapon). Yes I know, statblocks are secondary. Still, better then nothing, I guess?
2. Widly throuout the net it is assumed that Flurry of Blows is "An attack routine of a main hand with bonus attacks granted by class-feature itself". It isn't restricted to a single hand, just to a number of attacks your BAB and FoB give you.
   Frankly, the 'proof' here is the same as above, just read differently - the table entry taken literally. To me it was obvious, they just taken the simpliest case to place into a table (attack routine with no other bonus attacks than those, given by the class-feature, table entry was describing). But at least some people claim that without a declaration of intent we can't be sure what an intent was and we are left with what is actually printed in the table. Another 'proofs' are various FAQ entries, which expicitly allow natural attacks, for example, to be added after the Flurry of Blows in the same full-attack. I should point here, D&D 3.5 FAQ itself isn't without issues, so should be employed carefully.
3. Flurry of Blows consists of only those bonus attacks class-feature itself gives you, and all other attacks in a full-attack a monk makes are just regular attacks.
   "Proof" here, as I understand, is a passage, quoted above in my question (while it may, probably, also support point two of it). FAQ rulings are also mentioned to support this point of view.

I'm interested, what interpreation is correct? Maybe, there is some completely different forth one, I have failed to notice?

To spell it out as a single sentence:
Do restrictions (weapons used) and seems-to-be-a-bonus (full strength bonus on damage rolls) granted apply to all attacks, attacks called 'flurry attacks' by the table (i.e. all attacks excluding bonus attacks from sourses, other than Flurry of Blows itself), or just the bonus attacks?

Answer 1

All regular attacks, meaning the attacks granted by advancement in the base attack bonus table plus bonus attacks granted by utilising flurry of blows, made during your full attack action when using Flurry of Blows follow these rules:

1. Unarmed or Monk Weapons Only
2. All attacks get exactly 1x strength bonus

These restrictions only apply to attacks made for the 'regular' full attack action. Flurry of Blows makes no mention of interacting with other feats or abilities that might add additional attacks from the feat/ability, but would otherwise not be part of a normal BAB-based flurry attack routine.

Here's why:

When unarmored, a monk may strike with a flurry of blows at the expense of accuracy. When doing so, she may make one extra attack in a round at her highest base attack bonus, but this attack takes a -2 penalty, as does each other attack made that round.

Mostly flavor text, but it does establish two things. First, that there are multiple attacks in the flurry, and second, that only one extra attack is granted. The monk strikes with a flurry of blows and gets one extra attack when doing so -- by definition, the flurry is multiple attacks with an extra attack granted. Compare that to Snap Kick which is explicitly one extra attack whenever one makes attacks with other weapons.

[...] A monk must use a full attack action to strike with a flurry of blows.

This does not help much one way or the other

When using flurry of blows, a monk may attack only with unarmed strikes or with special monk weapons (kama, nunchaku, quarterstaff, sai, shuriken, and siangham).

This still does not help one way or another since "or"

She may attack with unarmed strikes and special monk weapons interchangeably as desired.

Now we are getting to some important distinction. Using Flurry of Blows explicitly grants only one extra attack, however this rule states that the monk may interchangeably use unarmed strikes and special monk weapons as desired when using Flurry of Blows. This means Flurry must be the entire attack action, otherwise a monk would be unable to interchangeably use weapons (at least until greater flurry, but that has not yet been discussed in the rules).

When using weapons as part of a flurry of blows, a monk applies her Strength bonus (not Str bonus × 1½ or ×½) to her damage rolls for all successful attacks, whether she wields a weapon in one or both hands. The monk can’t use any weapon other than a special monk weapon as part of a flurry of blows.

The key phrases here are "as part of a flurry of blows" and "for all successful attacks". If a flurry of blows was only a single bonus attack, this language would be entirely unnecessary.

In the case of the quarterstaff, each end counts as a separate weapon for the purpose of using the flurry of blows ability. Even though the quarterstaff requires two hands to use, a monk may still intersperse unarmed strikes with quarterstaff strikes, assuming that she has enough attacks in her flurry of blows routine to do so.

This makes reference to flurry of blows being a "routine" and also again references multiple attacks being made. Also note that the monk may "intersperse" strikes. If flurry of blows was only the bonus attack(s) granted by the ability rather than the full attack, , "alternate between" or some other verbage would be more appropriate. Intersperse implies 3 or more attacks possibly being considered, which is outside what is offered by the maximum of two bonus attacks granted.

One final point is that at no point in the feat's description does it say the weapon restrictions and strength rules apply only to attacks granted by flurry of blows. Instead, it repeatedly refers to attacks when using flurry of blows. Flurry of blows can therefore be most-reasonably assumed to be a replacement for the BAB attacks made when declaring a full attack action.

The short version of flurry is:

1. For the monk's full attack action, they may only use special monk weapons or unarmed
2. For the monk's full attack action, the monk gets +str to damage for all attacks
3. The monk gets one extra attack at maximum base attack bonus
4. All attacks for the round get -2 attack penalty
5. Any attacks added by other abilities and feats allowed in conjunction with a full attack action still work normally, separate from the flurry of blows maneuver, but are still affected by the penalty to attack.

Answer 2

The wording itself is ambiguous, which leaves the FAQ as the only evidence we have

As Wannabe Warlock’s answer discusses, flurry of blows refers to “when using a flurry of blows,” and talks about multiple attacks. At 1st level, flurry of blows only gives a single bonus attack, which makes concerns about, for example, switching up which weapon each attack is made with irrelevant—at 1st level.

It’s also true that the rules have not yet discussed multiple bonus attacks from flurry of blows at the point those plurals are used. But multiple bonus attacks are a part of flurry of blows, since greater flurry allows that at 11th. Flurry of blows does need rules for them, and it’s very common in 3.5e to put all the rules for something in its initial description, to keep any extension or improvement to a fairly minimal amount of text: in this case, greater flurry’s description can be just two short sentences.

So the use of the plural is not much evidence of anything. Hinging multiple knock-on effects on the use of a plural is a very bad idea for a large number of reasons, foremost being that there was good reason to use a plural here either way, but not insignificant is the considerable fact that 3.5e simply wasn’t edited to that level of strictness.

Barring that, there simply isn’t enough information to go on. We cannot say whether “when using flurry of blows” refers to the extra attacks that flurry of blows offers, or to the entire full-attack in which the flurry of blows is made, that is, 1 or 3. For that matter, 2 remains a possibility thanks to the table, because we really do have just that little to go on here.

Alongside all of this is the FAQ, which I’ll be the first to condemn as near useless. Nonetheless, the FAQ supports options 2 or 3, explicitly stating that secondary attacks with natural weapons can be made in a full-attack in which flurry of blows is used (and natural weapons are not special monk weapons and so cannot be used “when using a flurry of blows,” so those attacks would have to somehow not be considered part of that). Per the above, we have almost no solid, objective, RAW evidence—which leaves the FAQ as the best available evidence. Which isn’t worth much, but it’s worth more than “they discuss how multiple attacks work before getting to the line that explains when you get multiple bonus attacks, so they must be referring to the non-bonus attacks,” which is the only alternative argument I’m aware of. Even then, that argument is unclear about the status of other bonus attacks in the full-attack.

And finally, it’s a bit obvious and perhaps a bit tangential, but seriously, let’s also keep in mind that the monk is an extremely weak class. It needs all the help it can get.