meloliva14/verity-mcp

Verity MCP — verify before you act
The official Model Context Protocol server for VerityLayer: independent, fail-closed trust checks any MCP-capable agent can discover and call. Fact-check a claim, screen for prompt-injection, catch PII, and gate irreversible actions — each check returns a calibrated verdict and **abstains rather than guess**. Payment is pay-per-call via x402 (USDC on Base mainnet). Verity holds **no private key** and never charges silently.
> **Name note:** this is VerityLayer's official server — PyPI package verity-mcp, npm package @veritylayer/mcp. The *npm* package named verity-mcp is an unrelated third-party project.
Tools & pricing (every docstring states its price up front)
| Tool | Price | Grounded? | What it's for |
|---|---|---|---|
| quick_verify | **$0.02** | no (Haiku) | Cheap reality-check on a claim — **the loopable default**. Run everywhere, escalate the load-bearing ones. |
| grounded_verify | **$0.25** | yes (Sonnet, live web citations) | The default product — web-grounded with cited evidence, for facts that matter before you act on them. |
| pro_verify | **$0.35** | yes (Opus, premium synthesis) | The deepest tier — high-stakes claims where the grounded answer isn't confident enough to act on. |
| verify_receipt | **free** | — | Statelessly verify a signed Ed25519 verdict receipt — the audit trail / second opinion, no payment. |
| detect_injection | $0.02 | — | Screen untrusted text / tool output for prompt-injection before acting on it. |
| moderate_content | $0.02 | — | Is this safe to publish? (allow / review / block priced identically — no block-to-bill.) |
| redact_pii | $0.02 | — | Does this leak PII or secrets? Returns findings + a redacted version. |
| guard_action | $0.02 | — | **The money-line gate:** allow / review / block right before an irreversible action. |
Quickstart
With uv (recommended — Claude Desktop / any MCP client):
Or with pip:
That gets you the tools and the **free** verify_receipt. To get **paid verdicts**, read the next section — it's the part most people trip on.
How payment works
Verity's endpoints answer **HTTP 402 (Payment Required)** until the disclosed USDC micro-payment is settled. There are two ways to do that.
Wallet mode — get real verdicts (recommended)
Point VERITY_WALLET_KEY at a **funded Base-mainnet wallet** and this server settles each call itself — the paid tools return real verdicts. Your key never leaves the process: it signs an EIP-3009 authorization locally for the exact amount each challenge discloses, and Verity only ever receives the signature. Nothing is charged silently; every price is disclosed up front.
> **Use a dedicated, low-balance wallet.** This key can spend. Fund it with a few dollars of USDC on Base — calls cost $0.02–$0.35.
Keyless — the default
With no key set, this server holds nothing and pays nothing: a 402 is surfaced transparently (price restated, challenge attached) for an x402-capable caller to settle.
**Be aware of the honest caveat:** no shipping MCP client — Claude Desktop, Claude Code, Cursor, Windsurf — settles x402 today. So in keyless mode the paid tools will return payment_required and **no verdict**, forever. That's not a bug and it isn't hidden: the response says NO VERDICT WAS PRODUCED. Do not proceed as if this returned allow. If you want verdicts from an ordinary MCP client, use wallet mode.