Miraculous tools or Miraculous weapons are special omni-purpose tools that come with their respective Miraculouses. Whenever a Miraculous owner transforms, they possess a tool specific to whichever Miraculous they're wearing.
For the sake of seeing and communicating with kwamis, a mage in ancient times created the Miraculouses, magic jewels. At the same time of making Miraculouses, the mage created tools to go with each Miraculous.
Besides their Miraculous weapons, some wielders also can fight with additional weapons like Tentomushi with her nekode, La Coccinelle with her rapier, and Ladybug with Kagami's saber in "Riposte". Some weapons can split apart like Cat Noir's staff, showing that they are capable of dual-wielding.
When utilizing Unification, Miraculous holders can dual-wield both weapons, such as when Dragon Bug fought with both the dragon sword and the ladybug yo-yo.
Each tool is a different object, like Ladybug's yo-yo and Cat Noir's staff. These tools come in a great variety of different forms, including toys, musical instruments, and actual weapons. Usually, the tool is a size that can easily be carried by hand, and most tools can be worn when they aren't in use, such as Ladybug wrapping her yo-yo around her hips or Cat Noir having his staff attached to his back.
Sometimes, when fusion powers are used, Miraculous tools can change color, like how the mouse jump rope changed from pink to orange, red and black upon the Mouse Miraculous being fused with the Fox, Ladybug, and Cat Miraculouses, respectively. Also, the tool's appearance can change according to its user, as the Turtle Miraculous' shield has a different form when used by Carapace and Jade Turtle.
The tools are used as weapons, being incredibly handy for both offense and defense. The tools are indestructible; the only thing that can break them is the powerful magic of a miraculous, such as the Butterfly Miraculous power in Simon Says' command card, or the force of a Miraculous owners superstrength.
Some of the tools are capable of being used as a mode of transportation. An example of this is when Ladybug uses her yo-yo to swing from place to place, while Cat Noir can vault himself with his staff.
The tools also have technological features, including a phone, a GPS, and a search engine, among a number of other features.  The features of the Miraculous tools "update" in accordance with the technologies of the time.
It has been shown since that the Tools can be used as a breathing device underwater.
For some Miraculous holders, they need the tool to use their superpowers. For example, the Ladybug Miraculous owner tosses the yo-yo into the air when utilizing the Lucky Charm, the Fox Miraculous owner plays the flute to create Mirage, the Turtle Miraculous owner holds up the shield to engage Shell-ter, and the Bee Miraculous owner spins the spinning top and catches it to use Venom.
However, seen in "Sandboy", it appears that some of the tools have a weakness. When they are used to summon their powers, the holders can't use them to attack or defend themselves. If they are attacked during the process, the powers will be canceled out. If a holder becomes separated from their weapon, they can't summon their powers.
Some of the weapons are capable of storing and holding other things like tracers, ear communicators, or with Marinette storing letters in her purse, and they were moved into her yo-yo when she transformed in "Backwarder". When the yo-yo or staff is transformed into their phone mode, they are capable of taking photographs. When the holder is detransformed, the photographs will transfer to the holder's regular phone like with Adrien's phone in "Oblivio".
In "Cat Blanc", Hawk Moth is shown to be able to call for his Cane from afar. It could be possible that when a Miraculous holder gets older, they share a mental connection with their weapons. Some like Ladybug's yo-yo string is connected to their holder's willpower, even though it's used by young heroes. It could be possible that their mental connection grows with time. When under the powers of fusion, some weapons can be combined with other Miraculous superpowers. As seen in "Miracle Queen", Dragon Bug combined her yo-yo with the Water Dragon power to to make a spherical water shield.
When Théo Barbot and Chloé Bourgeois get akumatized into copies of Cat Noir and Ladybug respectively, they possess identical versions of the original superheroes' tools with the same features.
Lila Rossi's akumatization into a replica of a Fox Miraculous holder includes her possessing a copy of the flute.
The real flute in "Sapotis" has the same abilities as Volpina's flute, but Rena Rouge's flute can only create one illusion as opposed to Volpina's many illusions. After the flute has been used once, the Fox Miraculous starts to time out, but Volpina's Miraculous doesn't.
As depicted in art in "Ladybug & Cat Noir", Herakles had a spear and Tomoe Gozen had a naginata, although it's uncertain if these weapons are the tools to their unknown Miraculouses or additional weapons.
In "Reverser", "Queen Wasp", and "Mayura" it is revealed that the Miraculous tools can be used for breathing underwater, even if Cat Noir and Ladybug are not in aqua form.
Miraculous tools can also be destroyed by Cataclysm as seen in "Mayura".
Also hinted in "Mayura", Ladybug wanted to used Hawk Moth's cane to track him implying that Miraculous tools can be used to find their owners when lost, although Hawk Moth detransforms before they can.
In "Oblivio", it's revealed that the weapons when converted into their phone forms have a user's guide.
In "Miracle Queen", the tools can also be turned into akumatized and amokitized objects.