langchain-clearsigned

A LangChain tool that gives any agent an adversarial verify step: Clearsigned checks one factual claim against live web evidence and returns SUPPORTED, REFUTED or UNVERIFIABLE with a confidence that is a measured realized rate from a published calibration curve, every source with its stance, and an Ed25519-signed receipt this tool verifies offline against Clearsigned's pinned published key before any of it reaches the agent.

Each call pays $0.05 USDC over x402 (Base mainnet) from a key you hold. The price never depends on the verdict; refunds exist only for failure to deliver. UNVERIFIABLE is a real answer: the engine abstains rather than guesses.

Install

pip install langchain-clearsigned
export CLEARSIGNED_BUYER_KEY=0x…   # an EVM key holding a little USDC on Base mainnet

Use

from langchain_clearsigned import ClearsignedVerifyTool
from langgraph.prebuilt import create_react_agent

agent = create_react_agent(model, [ClearsignedVerifyTool()])
agent.invoke({"messages": [("user", "Is it true that the Eiffel Tower is in Paris? Verify first.")]})

The tool returns a JSON string:

{"verdict": "SUPPORTED", "confidence": 0.914,
 "confidence_meaning": "measured realized rate under engine-pkg-groq-20260925-n204",
 "evidence": [{"source": "https://en.wikipedia.org/wiki/Eiffel_Tower", "stance": "supports"}],
 "receipt_id": "…", "signature_verified_offline": true}

A receipt whose signature does not verify comes back as RECEIPT_SIGNATURE_INVALID and nothing from it is passed on. Verdicts take about 5 to 15 seconds.

Without a wallet

buy_verdict(claim, exchange=..., pinned=...) accepts an injected exchange function and pinned key, which is how the package's own tests run: no network, no wallet, receipts signed with a throwaway key through the production recipe.

How to check Clearsigned

• Pin the key at https://verify.clearsigned.com/pubkey (this tool does).
• Walk the public hash-chained receipt ledger at https://verify.clearsigned.com/ledger/verify.
• Live quality figures: https://clearsigned.com/quality · serving curve: https://clearsigned.com/stats.json.

Source of truth

Developed in the Clearsigned monorepo (products/langchain-clearsigned/) and mirrored to https://github.com/diawest82/langchain-clearsigned. Changes land in the monorepo first.