Principal AI Engineer

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 customers favorite story?

We're searching for a Principal Engineer, AI Modeling who'll be instrumental in advancing the AI models underpinning our customer service automation. This role involves enhancing AI performance through innovative techniques such as prompt engineering, fine-tuning, and the creation of advanced AI tools and workflows. By designing sophisticated agentic AI systems, the Principal Engineer elevates the reasoning and interaction capabilities of AI across intricate customer service processes. Collaborating with diverse teams, they ensure AI-driven enhancements are optimally integrated into production environments, thereby improving customer interactions and satisfaction. Overall, this position is crucial for the strategic enhancement of T-Mobile's AI capabilities, ensuring our customer service operations are both highly reliable and efficient.

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!

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.

Knowledge, Skills and Abilities:

• 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.

Preferred Knowledge, Skills, and Abilities:

• 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.

Education:

• Bachelor's degree in Computer Science, Artificial Intelligence, or equivalent
• Masters degree in Computer Science or Artificial Intelligence preferred

• At least 18 years of age
• Legally authorized to work in the United States

Travel:
Travel Required (Yes/No): No

DOT Regulated:
DOT Regulated Position (Yes/No): No
Safety Sensitive Position (Yes/No): No

Base Pay Range: $150,700 - $271,900

Corporate Bonus Target: 20%

The pay range above is the general base pay range for a successful candidate in the role. The successful candidate’s actual pay will be based on various factors, such as work location, qualifications, and experience, so the actual starting pay will vary within this range.

At T-Mobile, employees in regular, non-temporary roles are eligible for an annual bonus or periodic sales incentive or bonus, based on their role. Most Corporate employees are eligible for a year-end bonus based on company and/or individual performance and which is set at a percentage of the employee’s eligible earnings in the prior year. Certain positions in Customer Care are eligible for monthly bonuses based on individual and/or team performance. To find the pay range for this role based on hiring location, click here.

At T-Mobile, our benefits exemplify the spirit of One Team, Together! A big part of how we care for one another is working to ensure our benefits evolve to meet the needs of our team members. Full and part-time employees have access to the same benefits when eligible. We cover all of the bases, offering 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, and voluntary long-term care insurance. We don't stop there - eligible employees can also receive mobile service & home internet discounts, pet insurance, and access to commuter and transit programs! To learn about T-Mobile’s amazing benefits, check out www.t-mobilebenefits.com.

Never stop growing!
As part of the T-Mobile team, you know the Un-carrier doesn’t have a corporate ladder–it’s more like a jungle gym of possibilities! We love helping our employees grow in their careers, because it’s that shared drive to aim high that drives our business and our culture forward. By applying for this career opportunity, you’re living our values while investing in your career growth–and we applaud it. You’re unstoppable!

T-Mobile USA, Inc. is an Equal Opportunity Employer. All decisions concerning the employment relationship will be made without regard to age, race, ethnicity, color, religion, creed, sex, sexual orientation, gender identity or expression, national origin, religious affiliation, marital status, citizenship status, veteran status, the presence of any physical or mental disability, or any other status or characteristic protected by federal, state, or local law. Discrimination, retaliation or harassment based upon any of these factors is wholly inconsistent with how we do business and will not be tolerated.

Talent comes in all forms at the Un-carrier. If you are an individual with a disability and need reasonable accommodation at any point in the application or interview process, please let us know by emailing ApplicantAccommodation@t-mobile.com or calling 1-844-873-9500. Please note, this contact channel is not a means to apply for or inquire about a position and we are unable to respond to non-accommodation related requests.