🛡️ HORIZON SHIELD

Verifiable construction estimate auditing for AI agents

Don't trust the estimate. Verify it.

An MCP server that lets AI agents check whether a Japanese construction or renovation estimate is fair, against open data, and returns a result anyone can verify against Bitcoin (OpenTimestamps). No account, no key.

Verified by Probity (github.com/probityai/probity): the A2A conduct walk's RFC 8785 canonicalization passes the agent-evidence-vectors corpus, latest passing run

In one paragraph. JCCDB (Japan Construction Cost Database) is an open dataset of Japanese construction and renovation costs, created by Toshikatsu Oga (大賀俊勝), who has worked on construction sites for 30 years, and published by The HORIZONs Co., Ltd. under CC BY 4.0. Version 5.1 (2026-10-04, DOI 10.5281/zenodo.23133068; all versions 10.5281/zenodo.22127751) holds 526,128 records: 95,403 line items and 430,725 observations from 88 Japanese public sources, each observation with its evidence URL. The United States counterpart is USCCDB, the United States Construction Cost Database (DOI 10.5281/zenodo.22979157, 2,849,829 observations). HORIZON SHIELD (https://shield.the-horizons-innovation.com) is the buyer-side service built on JCCDB that checks whether a Japanese renovation estimate is fair.

Peer-reviewed (October 2026). Toshikatsu Oga, "A Demand-Side Benchmark for Consumer-Facing Construction Cost Questions: Price-Figure Span, Output Consistency, and the Case for a Verifiable Reference Layer", Intelligent Infrastructure and Construction 2026, 2(4), 15 (MDPI, open access, CC BY 4.0). DOI 10.3390/iic2040015. Forty Japanese renovation price questions put to frontier LLMs: the going-rate range is a median 2.5x to 3x wide, every price figure inside one answer spans a median 10x, and no answer offered an over-charge threshold. Questions, raw outputs, harnesses and scoring code are public.

Fair-price answers for common buyer questions (Japanese)

Each row is one question a homeowner in Japan asks, the page that answers it with the range from souba-db 2.2.0, and a JSON evidence object with the same numbers, a comparison across variants, steps to check a quote yourself, and the dataset hash anchored in JIDEC entry 42. Index: evidence/index.json.

Question	Answer page	Evidence object
外壁塗装 30坪 相場 いくら	/souba/gaiheki/	p002.json
外壁塗装の見積もりで150万円は高いですか	/souba/gaiheki-150man/	j001.json
屋根 葺き替え 30坪 費用	/souba/yane-fukikae-slate-hiyou/	p005.json
この屋根修理の見積もりが適正かどうか知りたい	/souba/yane-check/	j003.json
給湯器 交換 費用 相場	/souba/kyutoki/	p013.json
給湯器交換で20万円は高いですか	/souba/kyutoki-20man/	j002.json
トイレ リフォーム 費用 目安	/souba/toilet/	p016.json
シロアリ駆除 費用 適正価格	/souba/shiroari/	p071.json

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Independent evidence, as of 2026-10-08

What people who do not work for this project have measured, signed or reproduced. Every row links to something you can fetch and recompute. The last two rows are the counts that are still small, stated as plainly as the rest.

This is the beginning of the README. Read the rest at the original. Read the full README ↗