GMO Payment Gateway Becomes First Domestic PSP to Fully Launch "Payment Development Documentation" with LLM Exploration and AI Search Capabilities

GMO Payment Gateway, Inc. (TSE Prime: 3769, CEO: Kazunari Aiura, hereinafter GMO-PG), a leading comprehensive online payment service provider, announced the full public release of its "Payment Development Documentation" on March 30, 2026. This documentation is equipped with Large Language Model (LLM) exploration and AI search functionalities, a first for a domestic Payment Service Provider (PSP) within the "PG Multi Payment Service."

Following its initial announcement and limited release to select merchants and development companies on February 3, 2026, the documentation has undergone continuous improvements based on feedback from actual usage. This enhanced version aims to improve development efficiency and accuracy for existing merchants and development companies when implementing specification changes. For new companies adopting the "PG Multi Payment Service," the documentation is expected to expedite decision-making by allowing them to grasp specifications, connection methods, and anticipated implementation patterns from the initial consideration phase, thereby reducing the development burden during the design and implementation stages.

【Background and Overview】

As the utilization of generative AI expands, development sites are increasingly adopting LLMs for information exploration. Beyond the traditional method of referencing documents page by page, there is a growing trend of using AI as an auxiliary tool to cross-reference related information. In such explorations, developers input queries to AI, which then refers to the document content to generate answers. Consequently, it is crucial for documents to be structured in a way that is easily understandable not only by humans but also by AI.

Meanwhile, online payments in Japan are becoming increasingly complex due to the existence of diverse payment methods, including convenience store payments and QR code payments, in addition to credit card payments. Developers need to design systems that integrate payment functions by cross-referencing multiple conditions and prerequisites. Misinterpretations of specifications or omissions in references can impact quality and development schedules.

In response to these environmental changes, GMO-PG announced on February 3, 2026, its policy to redesign the document structure for LLM-based exploration and introduce AI search functionality (Note 1). This initiative aims to provide development documentation that combines a structural design for LLM web exploration with AI search capabilities, a first for a domestic PSP (Note 2). The full public release follows extensive improvements based on feedback from developers who participated in the early access period.

Developers of existing merchant services can achieve greater efficiency and accuracy when modifying specifications or adding new payment methods. Companies considering online payments can accurately grasp specifications, connection methods, and constraints from the initial consideration phase, and can also preview anticipated implementation patterns. This enables informed decision-making based on clear prerequisites for estimates and designs, leading to reduced rework and development burden in the subsequent design and implementation phases.

GMO-PG is committed to advancing Japan's payment development environment by providing operational expertise, cultivated through over 22 trillion yen in annual payment processing (Note 3), in a format suitable for the AI era.

(Note 1) Announcement on February 3, 2026: "GMO Payment Gateway Develops Payment Development Documentation with LLM Exploration and AI Search, First for a Domestic PSP" URL: https://www.gmo-pg.com/news/press/gmo-paymentgateway/2026/0203.html

(Note 2) First case combining a structural redesign for LLM web exploration with the introduction of AI search functionality by a PSP primarily serving the Japanese market. Source: GMO-PG research.

(Note 3) As of the end of December 2025, consolidated figures.

【Comments from Early Adopter Companies】

Gakuto Yamada, Project Manager, note, Inc.

From a developer's perspective, I reviewed the new manual. The addition of search functionality and an AI assistant makes it easier to find the necessary specifications and parameters, allowing for more efficient resolution of implementation questions.

The structure, which allows for in-depth exploration by use case and payment method, is also user-friendly. For those new to "PG Multi Payment Service," the clear progression from desired functionality to implementation methods makes it easy to grasp the overall picture.

The inclusion of language-specific samples and request/response examples in the API reference, along with a clearer transaction state transition diagram, are highly appreciated improvements that directly contribute to reducing development time.

The addition of "llms.txt" for AI reference is a timely initiative that aligns with current trends, and I look forward to its future development.

Takato Koshikawa, Manager, Makeshop Business Division Development Department, GMO MakeShop, Inc.

Previously, implementing payment integrations required cross-referencing multiple documents, consuming significant time for research.

The consolidation into the "PG Multi Payment Service Developer Documentation" allows for the completion of tasks from payment method selection to connection methods, API references, and use cases in one place, promising substantial reductions in implementation effort.

Such improvements in the development environment will ultimately translate to faster development of new features, enabling us to offer prompt introduction of payment methods aligned with market trends to "makeshop byGMO" users.

Furthermore, it is expected to contribute to shortening recovery times in the event of unforeseen issues. We highly value the ability to allocate more resources to initiatives that directly enhance customer experience while reducing development costs.

I feel that an environment has been created where developers can concentrate on their core design and implementation tasks, and I anticipate further enhancements in the future.

【Features of the Fully Released Documentation】
(URL: https://docs.gmo-pg.com/mulpay/ )

This documentation is structured around the following three key points:

1. Structural Design Assuming LLM Exploration

We have expanded use cases tailored to business models and operational requirements, organized basic information and a link collection for the "PG Multi Payment Service," and prepared the "llms.txt" format for LLMs. This creates an environment where AI can easily grasp the overall structure of the documentation.

Additionally, each page is available in "Markdown" format, providing structured text that LLMs can easily recognize. A "Markdown" copy function has also been implemented, allowing developers to easily paste it into AI prompts.

These features enable AI to better read the content after accessing the documentation, improving site readability. As a result, LLM-based information exploration will facilitate more relevant references to developer queries, leading to improved answer accuracy.

2. Implementation of AI Search Functionality

A search function has been implemented that allows for cross-referencing relevant information based on the content being considered or questions asked, independent of page structure or keywords. Furthermore, a new "Ask AI" function allows users to ask questions to an AI optimized specifically for this documentation. By using this documentation as the reference source, the AI generates answers based on an understanding of the specifications, supporting developer decision-making (Note 4).

(Note 4) Content entered into the "Ask AI" function may be shared with third parties involved in the operation and provision of this service, stored for a certain period, and used for purposes such as service provision and quality improvement. Please refrain from entering personal or confidential information.

3. Features Enhancing Developer Convenience

The API reference includes expanded sample codes and a function executable within the browser. By providing an environment where users can test functionality immediately, we have realized a "try it now" experience. The design allows for immediate transfer of acquired code to the user's own environment, contributing to faster verification in the initial implementation stages.

Furthermore, the documentation, previously provided across multiple independent websites for different purposes, has been consolidated into a single website. This structure facilitates easier access to desired information and allows for a seamless workflow from consideration to design and implementation.

Based on feedback from early adopter companies, this documentation has undergone improvements in usability and understandability, including UI enhancements for the API reference, expansion of sample codes, improved search response speed, and support for shortcut activation (Ctrl+K).

■ For detailed information on how to utilize this documentation and specific usage examples, please refer to "PX+ byGMO," our owned media that supports business growth starting with payments. We encourage you to visit.

Released Payment Development Documentation Supporting OpenAPI.

Introducing "PG Multi Payment Service Developer Documentation"

URL: https://www.gmo-pg.com/pxplus/journal/8233/

【About "PG Multi Payment Service"】
(URL: https://www.gmo-pg.com/service/mulpay/ )

This is a comprehensive online payment service that supports over 30 diverse payment methods, including credit card payments, convenience store payments, and QR code payments. It provides a flexible payment infrastructure tailored to the business model and growth phase of each merchant. The service adopts a development approach that facilitates design and implementation based on OpenAPI specifications, and features robust security and fraud detection functions, supporting online payments across a wide range of fields such as EC, digital services, and B2B transactions. Continuous efforts are also made to improve documentation and reference environments to ensure developers can accurately access the information they need.

【About GMO Payment Gateway, Inc.】

GMO Payment Gateway, Inc. offers services centered on payments that support online, cashless, and DX initiatives. With an annual payment processing volume exceeding 22 trillion yen, its comprehensive online payment service is adopted by over 150,000 merchants, including EC businesses and public institutions such as NHK and the National Tax Agency. As a leading company in the payment industry, GMO-PG drives social innovation through payment and financial technology, contributing to the realization of a sustainable society and its progress and development. This includes services such as comprehensive online payment services, in-person payment services, Buy Now Pay Later (BNPL), BaaS support for financial institutions and businesses, and strategic investments in overseas FinTech companies. (As of the end of December 2025, consolidated figures.)

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【Contact Information Regarding Services】

● GMO Payment Gateway, Inc.

　Innovation Partners Department

　TEL: +81-3-3464-2323

　Inquiries:
　https://contact.gmo-pg.com/m?f=790

【GMO Payment Gateway, Inc.】 (URL: https://www.gmo-pg.com/ )

Company Name: GMO Payment Gateway, Inc. (TSE Prime Market, Securities Code: 3769)

Location: Shibuya Fukuras, 1-2-3 Dogenzaka, Shibuya-ku, Tokyo

Representative: Kazunari Aiura, President and Representative Director

Business Activities:

■ Comprehensive payment-related services and financial services

Capital: 13.323 billion yen

【GMO Internet Group, Inc.】 (URL: https://group.gmo/ )

Company Name: GMO Internet Group, Inc. (TSE Prime Market, Securities Code: 9449)

Location: Cerulean Tower, 26-1 Sakuragaoka-cho, Shibuya-ku, Tokyo

Representative: Masatoshi Kumagai, Representative Director, Group Representative

Business Activities:

Holding Company (Group Management Function)

　■ Group Business Activities

　　Internet Infrastructure Business

　　Internet Security Business

　　Internet Advertising and Media Business

　　Internet Financial Business

　　Cryptoassets Business

Capital: 5.0 billion yen

Copyright (C) 2026 GMO Payment Gateway, Inc. All Rights Reserved.