Back to Blog In our last article, we shared the news about the beta launch of our AI Agent, “HSK CODE MASTER,” for HSK Code search. Today, we want to address one of the most frequently asked questions we received:
“I can get the HSK code quite well by putting simple items into GPT or Gemini.
Do I really need a separate service like HSK Code Master?”
It’s true that for commonly searched items (e.g., “What is the HSK code for roasted coffee?”), general-purpose Large Language Models (LLMs) like GPT or Gemini often provide reasonably accurate answers. However, can these generic LLMs handle item classifications for less common items, newly released products (e.g., smart coding blocks!), or complex items? You cannot rely solely on a general-purpose LLM for HSK codes, where accuracy is critical.
To understand where general LLMs fall short, we conducted direct comparisons between their performance and that of HSK CODE MASTER across various items. Below, we share the analysis results comparing Google’s Gemini 2.5 Pro (currently considered the most powerful inference model), the widely used GPT-4o, and HSK Code Master.
HSK CODE MASTER is the Only One Reflecting the Perspective of the Korea Customs Service
While GPT and Gemini occasionally provided accurate answers for simple items, they showed clear limitations when detailed classification or inference was required.
Even Gemini 2.5 Pro, specialized in inference, often provided non-existent codes, codes that disregarded usage-based sub-classification, or codes that did not reflect the specific perspective of the Korea Customs Service. Today, we will take a detailed look at one such case.
TEST CASE: Vanilla Extract for Baking
| Core Question: Does the classification apply the Korea Customs Service’s standard to vanilla extract? |
We asked the three services the same question: “What is the HSK code for vanilla extract for baking?” and received the following results:
| AI Service | Suggested HSK Code | Correctness |
| GPT-4o | 3302.10.1000 | ❌ Incorrect |
| Gemini 2.5 Pro | 3302.10.1000 | ❌ Incorrect |
| HSK Code Master | 1302.19.9091 | ✅ Correct |
At first glance, one might assume the code suggested by Gemini and GPT-4o is accurate since they match. However, according to the standard set by the Korea Customs Service, the correct code is “1302.19.9091.”
What Determined the Correct Answer?
The core issue in this case is whether to classify vanilla extract as a ‘perfumery preparation (function)’ or as a ‘vegetable extract (essence).’
- GPT/Gemini’s Incorrect Answer (3302.10.1000): This code falls under HS Heading 3302, which covers ‘preparations based on odoriferous substances.’ Generic LLMs likely focused on the ‘fragrance-imparting function’ from the words ‘vanilla’ and ‘baking,’ leading them to suggest this code. However, Heading 3302 strongly emphasizes ‘preparations’—substances mixed or diluted with other perfumery materials. An example would be blending vanilla essence with strawberry essence to create a new ‘strawberry milk fragrance.’
- HSK Code Master’s Correct Answer (1302.19.9091): In contrast, HSK Code Master accurately identified the item’s essence as a ‘vegetable extract’ obtained from the plant (vanilla bean).
| The Korea Customs Service’s Perspective: The Principle of Essential Character |
Derivation Process for the Correct Code 1302.19.9091
HSK CODE MASTER follows this principle, navigating the following logical steps to find the accurate code:
Step 1 (Selecting the Correct ‘Heading’)
The essence of vanilla extract is a vegetable extract, classifying it under HS Heading 1302.
Step 2 (Sub-heading Specialization)
Within HS Heading 1302 (Vegetable saps and extracts), items with high trade volume or special management needs are assigned specific subheadings. Vanilla extract does not fall under 1302.11 through 1302.14, so it is classified under 1302.19.
- 1302.11: Opium
- 1302.12: Extracts of liquorice
- 1302.13: Extracts of hops
- 1302.14: Extracts of pyrethrum or of the roots of plants containing rotenone
- 1302.19: Other vegetable saps and extracts
Step 3 (Determining the HSK 10-Digit Code – Korean Standard)
Now, the domestically specialized 10-digit code must be found under the 1302.19 code.
- Checking domestic databases like the Customs Law Information Portal confirms that various items under 1302.19 are assigned separate codes based on domestic needs.
- Among them, 1302.19.9091 is clearly specified with the commodity description: ‘Vanilla oleoresin or vanilla extract.’
- Having verified the precise case, the code 1302.19.9091 is finalized and provided to the user.
Why Did Gemini and GPT Provide Incorrect Answers?
Our team’s tests repeatedly showed that GPT and Gemini tended to retrieve codes found in general internet search results rather than verifying them against official Korea Customs Service standards. Although Gemini 2.5 Pro, compared to GPT-4o, possesses step-by-step reasoning abilities for complex questions, as a generic language model, it lacks sufficient training that HSK code searches must strictly adhere to the Korean Customs Service’s criteria, inevitably limiting its ability to provide accurate HSK codes.
Why is HSK Code Master’s Accuracy High?
HSK CODE MASTER’s high accuracy is based on a Retrieval-Augmented Generation (RAG) architecture that incorporates Sequential Thinking.
Semantic Vector Search
When a user submits a natural language query, the system first uses embedding-based vector search to find the most semantically similar cases from over 60,000 high-quality validation data points. This goes beyond simple keyword-matching services to capture contextual similarity.
Agentic Inference
Based on the retrieved content, an AI Agent—designed to act like a customs broker—generates the most probable candidate HSK codes by comprehensively considering the item’s material, function, purpose, and relevant regulations.
Verification and Enhancement
- External Data Cross-Verification: The generated code candidates are cross-checked using web searches to see how they have been applied in official external data sources, such as binding rulings or precedent cases from the Korea Customs Service, enhancing reliability.
- Internal Logic Verification (Sequential Thinking): The AI explicitly outlines the inference process step-by-step, verifying the code candidates itself. Through a “Chain of Thought” process—for example, “The essence of this item is a vegetable extract, therefore it should be classified under Heading 1302″—it self-corrects logical leaps or errors and derives the final result.
This multi-layered approach minimizes the hallucination problem inherent in generic LLMs, ensuring the trustworthiness of HSK CODE MASTER’s answers.
Conclusion
Today, we explained the accuracy of HSK CODE MASTER through a test case. Our team plans to share various other cases we have tested periodically.
HSK CODE MASTER is currently in open beta, where we are verifying answers and developing the service with various practitioners in the field. Experience for free how the Customs Broker Agent can streamline your HSK code search tasks and share your valuable feedback.
Experience HSK CODE MASTER now and let us hear your opinions!
