Agate is a recurring antagonist in the animated series and holds the position of an administrator within the Explorers, a secretive organization that serves as a primary antagonistic force. Her name is derived from the gemstone agate, continuing the organization's naming motif based on minerals and crystals. She is a woman with brown hair and black eyes, and her overall demeanor is consistently calm, collected, and observant. Unlike some of her more impulsive colleagues, Agate prefers to remain on the sidelines and analyze situations, choosing not to act unless it is strategically advantageous.

Within the internal hierarchy of the Explorers, Agate is closely aligned with another administrator named Spinel, effectively acting as his right hand. She specializes in information gathering, espionage, and subterfuge, often working behind the scenes to achieve the organization's goals. Her intellectual curiosity is reflected in her interest in Occulture, a magazine that explores mysterious and often fantastical subjects, though she personally remains skeptical of its more outlandish claims. While she maintains a calm exterior, she can be critical and sarcastic toward allies who fail their missions, including Spinel and a fellow administrator named Amethio.

Agate's role in the story expands significantly as she engages in numerous operations against the protagonists. She participates in a major mission to summon and capture the Black Rayquaza using a machine that mimics the energy of the legendary Pokémon Terapagos. Demonstrating her aptitude for infiltration, she later assumes a false identity as a teacher at Naranja Academy, even forging enrollment documents for her colleagues Coral and Sidian to pose as students, in order to gather intelligence and steal data related to Terapagos. During this arc, she develops a particular intellectual rivalry with the character Dot, clashing with her on multiple occasions both in direct confrontations and in strategic information warfare.

As the series progresses, Agate is shown to be a loyal supporter of Spinel's ambitious goals, helping him monitor targets and participating in plans to eliminate rivals like Amethio from the Explorers. However, her character reveals hidden depths beyond her cold and calculating nature. It is revealed that she was once a kind and dedicated schoolteacher whose school was forced to close due to a lack of funding. She was recruited into the Explorers by a man named Hamber, who promised her the means to earn enough money to one day build a new school. This backstory provides a strong motivation for her actions, as she sees her cooperation with Spinel as a necessary alliance to achieve her personal dream. Despite this partnership, she has subtly expressed discomfort with the ruthless extremes Spinel is willing to go to as he consolidates power, and another character has noted that she has changed significantly since beginning to work with him.

In battle, Agate is a capable Trainer whose known partner Pokémon is a Medicham. Like its Trainer, Medicham has a calm and reserved disposition and is used for both combat and reconnaissance, with its psychic abilities being employed for surveillance. During a climactic battle in the Laqua arc, Agate demonstrates her full power by using a Mega Stone to Mega Evolve her Medicham, gaining a significant advantage against a formidable opponent. This event highlights her strength as a Trainer and her willingness to use any means necessary to achieve her objectives.