Mission name: Magpies, Shiny Thieves
Mission rank: B
Objective: Take down the leader of the Magpies
Location: Kumogakure No Sato Widerness
Reward: 300
Mission description: The magpies, once known as the toughest bandits out there, have been stealing the tobacco of a town just outside of Kumogakure no sato. Their leader is said to have a hideout in a tree that has been hollowed out. There are two guards outside of the tree, and little is known about who is inside. The guards seem to be no problem. Your mission is to capture or kill the leader of the Magpies and thereby bring him to justice.
Mission details: The Magpies are known for more than stealing just tobacco, but that is where the robbers were last seen. They have two guards of Genin rank that are not too hard to take out at the door. They can only use academy jutsu and are of little threat to the person, but will alert those inside if given the chance.

The magpie is guarded by two other guards inside of his tree-house, and is located down in the roots in an underground base that they burrowed in the tree. If the ninjas go up they are met by a taijutsu master that will most certainly give them a run for their money. If the genin-guards get a yelp out, they are attacked by the taijutsu master after a short while.

When the ninjas descend into the tree, they must first face a lightning (raiton) user and then an earth (Doton) user. If they make a ruckus going down the stairs they encounter both at once.

The leader of the magpies is a Bukijutsu user that also uses restraint type jutsu on his opponents of Doton or Suiton type.

Name: Shin Douten
Age: 21
General Appearance:
Personality: Aggressive and overconfident
Motivations: Money
Fears: Spiders
Abilities: Can use Taijutsu at an A rank, but cannot use other Jutsus.
Other: If one calls attention to his stature, or his brutishness, he flies into a rampage. Using a B strength jutsu or 3 C rank jutsu will incapacitate him. He can be reasoned with if he thinks that it is a good deal, but not if he is alerted by the Genins below. He has A rank Strength and Endurance, but all other stats are D-3.

Name: Fu Sho
Age: 19
General Appearance:
Personality: Arrogant and sly
Motivations: Girls, especially pretty ones
Fears: Rejection by his friends or girls
Abilities: Able to use B rank Suiton jutsu and C rank Raiton Jutsu.
Other: Pretty unassuming, he only has C-0 rank stats, but his jutsu are deadly and precise.

Name: Lun chi
Age: 17
General Appearance:
Personality: Known Sociopath (no emotions)
Motivations: Blood and broken bones
Fears: Being broken herself.
Abilities: Able to use B rank Doton jutsu and has B ranked endurance, all of her other stats are D-2
Other: She will laugh openly at other's pain and use it to battle them with psychological warfare.

Name: Magpie Sonu
Age: 23
General Appearance:
Personality: A thief and a crook to the very end, will try to persuade anyone who is powerful to join his organization.
Motivations: Power, wealth.
Fears: Loss of life, he values himself above all others.
Abilities: Use of Doton and Suiton B rank jutsu to capture his opponents, and then ends their life with a swift cut to the neck with an elongated curved dagger.
Other: When the people that are there to capture him enter the room, he will offer them riches beyond their wildest dreams if they join the organization. If they accept, they fail the mission. If they do not he will try to kill them. If he is beaten, or unable to fight, he will cry and try to bargain for his life. Has B ranked stats across the board, but A rank Speed.

"If the genin-guards get a yelp out, they are attacked by the taijutsu master after one post."
And if you're the type to do a single post mission? Remove the bit about after one post, and just say combat will be initiated with him.

Other than that, your mission looks pretty good.