How Post-Classification Trade Flags Works
BetaThe checks that follow a settled HTS code: Chapter 99 trade-remedy provisions whose U.S. notes list the code, partner government agency requirements, and antidumping/countervailing duty orders whose scope cites it.
Beta. This skill is live, but it has not been certified by Proofwork yet.
The approach
The skill connects to your LLM workspace (Claude, ChatGPT, or any MCP-compatible environment) as an MCP server. It returns reference data, evidence, and instructions for each step. Your LLM does the reasoning.
Proofwork is never in the inference path. The server handles deterministic work — lookups, retrieval, and evidence construction — while the host LLM makes each decision.
Workflow
Available tools
Chapter 99 provisions whose U.S. note lists this code, with the note citation, the country named and the duty text
check_trade_remedies_payload
Partner government agencies whose published import requirements reach this code's chapter or heading
check_agency_requirements_payload
Antidumping and countervailing duty order notices whose published scope cites this code
check_addcvd_exposure_payload
Where the data comes from
USITC Harmonized Tariff Schedule — Chapter 99 U.S. notes
United States International Trade Commission
As of 2026-09-21
The Chapter 99 U.S. notes PDF from the current release: 2026 HTS Revision 19, 818 pages. The code lists that attach a provision to an article are mined from the notes' own sentences: a list is attached only when the note names the provision it belongs to, so a mislabelled subdivision drops out rather than mis-attaching thousands of codes. 56 lists covering 11,639 codes resolved; 52 lists remain unattached and are reported as unresolved rather than guessed at.
https://hts.usitc.govTerms: U.S. Government work; USITC publishes the HTSUS in the public domain.
USITC Harmonized Tariff Schedule — Chapter 99 rows (JSON export)
United States International Trade Commission
As of 2026-09-20
The Chapter 99 provisions themselves, with their duty text.
https://hts.usitc.gov/reststop/exportList?from=9901&to=9999&format=JSON&styles=falseTerms: U.S. Government work; public domain.
Federal Register API — ITA antidumping / countervailing duty order notices
Office of the Federal Register (NARA) / International Trade Administration
As of 2026-09-21
301 order notices indexed, 308 texts read. This is an exposure index built from the codes a published scope happens to cite — it does not track whether an order is still in force, and it is not a scope determination.
https://www.federalregister.gov/api/v1/documents.jsonTerms: U.S. Government work; Federal Register content is public domain.
Agency-published U.S. import requirements (chapter/heading level)
U.S. Customs and Border Protection and the partner government agencies
As of 2026-09-21
Authored from each agency's published import-requirement pages. This is NOT the CBP ACE HTS flag file, which is the authoritative per-code source and is not published as open data — so these flags are a prompt to check, never a statement that a filing is or is not required.
https://www.cbp.gov/trade/programs-administration/entry-summary/pgaTerms: U.S. Government works; agency regulations are public domain.
The data ships as a point-in-time snapshot. Every tool response states the revision it answered from; confirm anything you act on against the current published source.
What this skill does not determine
- Whether an antidumping or countervailing duty order actually covers your product. Scope is decided by the product description in the order, not by an HTS code; the codes a scope cites are explicitly non-dispositive. This is exposure, not scope.
- Whether an order is still in force. Revocations and sunset reviews are not tracked.
- Whether a partner government agency filing is actually required for your entry. The authoritative per-code source is CBP's ACE HTS flag file, which is not open data.
- Which provision to report when several attach to one code, or how duties stack. The tools list what attaches; the notes make some of them mutually exclusive.
- Whether a Section 301 exclusion applies. An exclusion is a product description, and a code alone cannot say whether one covers your product.
- The duty rate owed on an entry, or anything about a jurisdiction outside the United States.
Known limitations
- Nothing here has been through the eval harness. What has been checked, against sources independent of how this data was built: the Chapter 99 linkage against the lists USTR itself publishes (List 1 recall 0.911, List 2 0.923, the gap explained by HS-2022 renumbering — 59 of 73 missing codes no longer exist), and the agency flags against the two agencies that publish an HTS-keyed list — NOAA NMFS recall 0.919, DEA recall 0.425. The DEA result is a known defect: 103 of the 179 codes CBP publishes are missed, across 52 headings, so a quiet answer for a precursor chemical, plant material or laboratory equipment is not evidence that no requirement applies.
- Six note lists, covering 926 codes, could not be attached to a provision on the note's own wording and are reported as unresolved rather than guessed at. The AD/CVD index cannot be independently verified at all: every external roster is keyed on the ITA case number, which this index does not carry.
- Chapter 99 changes constantly — new provisions, exclusions that expire, orders that are revoked. Confirm anything that decides duty against the current HTSUS and the Federal Register before relying on it.