Project Lion - Senior Prompt Engineer - Japan (Remote, Part-Time)

Welo Global; United States; Remote; USD 57,000 - 95,000; Full time

Job summary

Welo Global is seeking a Prompt Engineer to own the end-to-end technical migration workflow for transitioning templates to LLM autoraters. You will use internal tools to maximize model performance and ensure high-quality prompts for complex template architectures.

Based in Japan, you will draft, test and refine prompts, monitor tooling outputs, and document launch readiness. Strong collaboration and analytical skills are required to succeed in this role.

Qualifications

• 4+ years as a Prompt Engineer with LLMS tuning for structured outputs.
• Proficiency in SQL or data analytics and model performance analysis.
• Excellent verbal and written communication skills.
• Native Japanese, fluent English; based in Japan.

Responsibilities

• Create baseline prompts with Automatic Prompt Generation (APG) for complex templates.
• Run and supervise Automated Prompt Optimization (APO) tools and review outputs.
• Manually draft, test and refine prompts for complex templates and edge cases.
• Monitor shadowbot runs, register disagreements, and track results.
• Compare prompts against gold data and measure accuracy (F1, precision, recall).
• Draft Launch Certification Documentation for final release.

Skills

Prompt engineering

SQL / data analytics

Communication skills

Bilingual: Japanese / English

Education

CS / DS / CL / HCI degree

Tools

Goose API

APG tooling

APO systems

Job description

We are seeking a Prompt Engineer to be responsible for the end-to-end technical migration workflow for transitioning templates to LLMautoraters. The role is required to use client’s internal tools to leverage prompt engineering techniques to maximize model performance.

Responsibilities:

Utilize Automatic Prompt Generation (APG) tools to create baseline prompts for complex parent-child template clusters.Run and supervise Automated Prompt Optimization (APO) tool, review the outputs, and flag when the APO reaches deadlocks or plateaus.Manuallydraft, test, and refine prompts to navigate complex template architectures, overcome anti-patterns, and handle edge cases where tooling is lacking or broken. Solve edge-case scenarios by designing and refining manual prompts.Monitorshadowbotruns to ensure sufficient disagreements (between human and LLM ratings) are registered, generated, and tracked.Run prompt versions against established gold data to continuously measureautoraterquality against the human crowd baseline, calculating accuracy metrics such as F1 scores, precision, and recall.Draft technical launch readiness justifications (Launch Certification Documentation) for final.

Requirement:

Language Skills: Native fluency in Japanese and fluent in English.Location: Must be based in Japan.Education: Bachelor’s, Master’s, or Doctorate degree in Computer Science, Data Science, Computational Linguistics, Human-Computer Interaction (HCI), Cognitive Science, ora relatedanalytical field.Prompt Engineering & AI Expertise: At least 4 years' experience as Prompt Engineer. Proven experience tuning Large Language Models (LLMs)for strict, structured outputs, complex classification tasks, and familiarity with chain-of-thought and few-shot learning.Data Analysis: Strongproficiencyinidentifyingerror patterns, analyzing model performance, and using SQL or other data analytics tools.Technical Agility: Ability to quickly learn and master proprietary tools with minimal supervision.Communication: Excellent verbal and written communication skills.

Optional / Preferred Skills:

Familiarity with enterprise-grade LLM interfaces like the Goose API.Experience in AI model evaluation, data science, computational linguistics, or software engineering.Hands-on experience with Automated Prompt Optimization (APO) systems or tuning workflows.Linguistic expertise, including an understanding of semantics and logic.