Principal AI Engineer

T-Mobile • Frisco, TX

20h

About The Position

At T-Mobile, we invest in YOU! Our Total Rewards Package ensures that employees get the same big love we give our customers. All team members receive a competitive base salary and compensation package - this is Total Rewards. Employees enjoy multiple wealth-building opportunities through our annual stock grant, employee stock purchase plan, 401(k), and access to free, year-round money coaches. That’s how we’re UNSTOPPABLE for our employees! Are you ready to be a part of powerful customer-centric AI at the Un-carrier and be the voice turning data into our customer’s favorite story? We’re looking for a Principal AI Engineer to lead the evolution of T-Mobile’s Agentic Next Best Action (ANBA) capabilities—powering intelligent, real-time decisioning and enabling the next best customer experiences at scale. In this role, you will design and optimize agentic AI systems that determine and execute the most effective next action for each customer interaction, while shaping seamless, personalized experiences. Leveraging techniques such as prompt engineering, fine-tuning, retrieval-augmented generation (RAG), and tool-integrated reasoning, you’ll build AI that dynamically orchestrates workflows, invokes APIs, and adapts decisions based on context and intent. You’ll work across engineering, product, and business teams to embed ANBA-driven intelligence into production systems—delivering proactive, outcome-oriented experiences that improve customer satisfaction and business results. This role is critical to advancing T-Mobile’s AI capabilities from traditional automation to autonomous, decision-driven systems that continuously learn and optimize both actions and experiences. We pride ourselves on encouraging a culture of innovation, advocating for agile methodologies, and promoting transparency in all that we do. Join us in embodying the spirit of the 'Un-carrier' and make a tangible impact! If you are passionate about driving excellence and want to make a significant impact, apply today!

Requirements

• Deep expertise in LLM fine-tuning and prompt engineering (e.g., OpenAI APIs, Hugging Face, Anthropic Claude, Google Gemini).
• Strong experience with AI orchestration tools (e.g., LangChain, LlamaIndex, vector databases for retrieval augmentation).
• Hands-on knowledge of function calling and API-based reasoning models (e.g., using structured outputs to drive automated workflows).
• Proficiency in Python and AI development frameworks for building scalable AI applications.
• Understanding of multi-agent architectures and best practices in agentic AI design.
• Experience with real-world AI evaluation techniques, including golden sets, synthetic data generation, and interactive testing.
• Ability to collaborate across teams, working with engineers, product managers, and conversational designers to refine AI-driven solutions.

Nice To Haves

• Experience in customer service AI applications, particularly intent-driven automation.
• Familiarity with RAG pipelines and vector database retrieval for augmenting AI responses.
• Background in AI middleware development, such as AI-powered function calling and API integrations.
• Knowledge of cloud AI services (AWS/GCP/Azure) and scalable AI architectures.

Responsibilities

• Architects agentic AI systems that accomplish sophisticated tasks by invoking AI models as well as internal and third-party tools using APIs, ensuring flawless data flow in production environments.
• Optimizes performance of agentic AI systems through prompt engineering, fine-tuning and reinforcement learning using T-Mobile’s customer interaction data.
• Develops and maintains supporting software components and scripts to enable AI model deployment, testing, evaluation and monitoring.
• Implement retrieval-augmented generation (RAG) techniques to ensure AI responses are contextually accurate and grounded in real-time data.
• Stay at the forefront of LLM advancements, incorporating the latest techniques in prompt design, few-shot learning, Tool integration protocols like MCP and AI orchestration frameworks like Agent SDK.
• Collaborates with backend engineers, business experts and conversation designers ensuring AI-driven enhancements are optimally integrated into production environments.
• Defining success metrics that aligns with business requirements and continuously evaluate and improve model quality based on those metrics.
• Participates in other duties or projects as assigned by business management as needed.

Benefits

• medical, dental and vision insurance
• a flexible spending account
• 401(k)
• employee stock grants
• employee stock purchase plan
• paid time off and up to 12 paid holidays - which total about 4 weeks for new full-time employees and about 2.5 weeks for new part-time employees annually - paid parental and family leave
• family building benefits
• back-up care
• enhanced family support
• childcare subsidy
• tuition assistance
• college coaching
• short- and long-term disability
• voluntary AD&D coverage
• voluntary accident coverage
• voluntary life insurance
• voluntary disability insurance
• voluntary long-term care insurance
• mobile service & home internet discounts
• pet insurance
• access to commuter and transit programs

What This Job Offers

• Job Type: Full-time
• Career Level: Principal