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EVIDIQ Assay

A signature is irreversible, and hex is unreadable. Assay turns calldata, an EIP-712 payload, or an unsigned transaction into a plain-language statement of what it will do — unwrapping multicall and execute wrappers to reach the call that actually matters — and flags the parts worth refusing.

Quickstart

Connect the Streamable HTTP MCP endpoint, then preflight for free before paying.

claude mcp add --transport http evidiq-assay https://mcp.evidiq.dev/assay/mcp

Or probe the public pricing discovery endpoint:

curl -s https://mcp.evidiq.dev/assay/x402

Prefer a Skill file? Fetch the agent-readable EVIDIQ Assay Skill:

curl -s https://mcp.evidiq.dev/assay/skill.md

What Assay is for

Ten MCP tools

Five free tools cover discovery, preflight, and offline verification. Five paid tools handle decoding, allowance analysis, simulation, counterparty screening, and attestation.

Paid analysis

• decode_transaction — Decode calldata, EIP-712, or an unsigned transaction into plain-language intent, unwrapping multicall and execute wrappers to reach the inner call. (0.005 USDT0)
• assess_approval — Allowance analysis: unlimited or excessive amounts, setApprovalForAll, Permit and Permit2 grants, and the spender's existing on-chain allowance. (0.01 USDT0)
• simulate_transaction — Simulate against a pinned block and report net asset deltas per address. (0.015 USDT0)
• screen_counterparty — Bytecode-level screening: proxy and upgradeability slots, owner privileges, mint, pause, blacklist and fee-setter surface, and whether any code exists at all. (0.02 USDT0)
• attest_intent — Bind the decoded intent and verdict to a content digest, sign it with EIP-191, and anchor the digest. (0.03 USDT0)

Free preflight and verification

• assay_capabilities — Rule catalog with severities and which rules are heuristic, plus supported chains, selector-set version, limits, and full pricing. (free)
• validate_payload — Parse-check the payload and return the detected kind and counts by severity — without the findings, and without charging. (free)
• estimate_cost — Quote one paid tool, or the whole price table when no tool is named. (free)
• verify_assay_report — Recompute the report digest and verify its EIP-191 signature offline. (free)
• get_artifact — Retrieve a stored report or attestation by id, within its TTL. (free)

What it accepts

Raw calldata, an EIP-712 typed-data JSON document, an unsigned transaction JSON, or a plain message. The kind is detected rather than declared, and validate_payload reports which kind it read before you pay. A payload it cannot parse is never scored as safe.

# calldata: approve(spender, 2^256-1)
0x095ea7b3000000000000000000000000<spender>ffffffff…ffff

Recommended workflow

Settlement happens before a paid tool runs, so a malformed argument is still a paid call. Preflight for free first.

1. Call assay_capabilities for the rule and selector set versions, chains, and prices.
2. Call validate_payload — it returns the detected kind and counts by severity for free.
3. Decode with decode_transaction; for an approval, add assess_approval.
4. Check the net effect with simulate_transaction, and the target with screen_counterparty.
5. If a counterparty needs proof, call attest_intent and hand over the report.
6. Verify offline with verify_assay_report, and re-fetch with get_artifact while its TTL lasts.

What a report proves, and what it does not

A report proves that these exact bytes, under this selector set and rule set version, decode to this intent and produced these findings. Anyone can re-run it and compare digests. It does not prove a transaction is safe to sign: simulation reflects one pinned block, some rules are explicitly heuristic and marked as such, and an unknown selector is reported as unknown rather than assumed harmless. Credentials are refused outright — a private key or mnemonic in the input is an error, and nothing is stored, attested, or anchored.

{
  "engine": "EVIDIQ-Assay/1.0",
  "selectorSetVersion": "1.0.0",
  "chain": "eip155:196",
  "intent": "Approve <spender> to move an unlimited amount of <token>",
  "findings": [
    { "rule": "UNLIMITED_APPROVAL", "severity": "high", "heuristic": false }
  ],
  "integrity": { "algorithm": "SHA-256", "digest": "...", "signature": "0x...", "signer": "0x..." }
}

x402 pricing

Payments use x402 v2 exact scheme with USDT0 (6 decimals) on X Layer (eip155:196). Verification and settlement run through the official OKX Onchain OS Payment SDK (@okxweb3/x402-core and @okxweb3/x402-evm). The OKX facilitator verifies each authorization and settles it on X Layer before any decoding runs.

Licensing

EVIDIQ owns and licenses its original Assay code under MIT. Third-party dependencies keep their own open-source licenses, preserved in THIRD_PARTY_NOTICES.md.

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