Senior AI Agent Engineer - AI Agent Development Section, Business Support Development Department (BSD)

Job Description:

Business Overview

Rakuten is one of the leading E-commerce companies in the world. Our mission is to empower people and society through the internet while aiming at becoming the "Global Innovation Company."

Department Overview

The Business Support Development Division (BSD) plays a crucial role in supporting various business operations that occur between users, clients, and Rakuten businesses from a systems perspective. Our division provides diverse services across four key domains: DATA, Business Support/Accounting, CRM, and AI Agent, which builds the foundation for leveraging AI across the entire Rakuten organization. We are committed to pursuing business process optimization and efficiency while delivering high value through our system offerings.

AI Agent Development Section, established under BSD in January 2026, is dedicated to building next-generation AI agent frameworks that empower Rakuten’s diverse business units through AI technology.

Our mission is to reshape the digital future of e-commerce by building AI-native solutions that empower Rakuten merchants, catalyze new revenue growth, and radically reduce operational costs.

Our main goal is to unify Merchant Communication Services

Consolidating fragmented communication services into a single, cohesive merchant interface to streamline communication and user experience.

Position:

Why We Hire

We are looking for an AI Agent Engineer to design and build autonomous AI systems that can perform complex tasks by interacting with tools, APIs, and environments. You will be at the forefront of AI development, moving beyond simple chatbots to create intelligent agents that drive business value.

Position Details

Design and develop autonomous AI agents using LLMs and agentic frameworks.

Build tool-use capabilities (Function Calling) for agents to interact with external systems and databases.

Optimize agent workflows for reasoning, planning, and task execution accuracy.

Evaluate and refine agent performance through rigorous testing and prompt engineering.

Work Environment

Mandatory Qualifications:

・ 7+ years of hands-on experience in web application design, code reviews, performance tuning, and architectural improvements.

・ 7+ years of experience in application development with a focus on database schema design and integration with external systems.

・ Extensive hands-on experience (7+ years) in the design and development of Web APIs.

・ 7+ years of experience in the development and operation of large-scale systems using Java (Spring Boot)

・ Experience with LLM orchestration frameworks such as LangChain, LlamaIndex, CrewAI, or Microsoft AutoGen.

・ Understanding of Prompt Engineering and Chain-of-Thought (CoT) reasoning techniques.

・Professional working proficiency in Japanese or higher.

Desired Qualifications:

・ Experience of management for large scale projects

・ Experience in evaluating agent performance using automated testing frameworks.

・ Knowledge of LLM performance optimization (latency reduction, cost management).

Other Information:

Additional information on Location

Tokyo

Additional information on English Qualification

・ TOEIC score of 800+ or equivalent business-level English proficiency.

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