Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@pcrzero-mcp Verify this receipt and tell me if it's valid."
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
Issue and verify signed receipts for agent actions from any MCP-speaking agent. PCRZERO adjudicates an attestation document against a policy and hands back a cryptographically signed receipt pair — durable, independently checkable proof that this decision was made, by these keys, over this document. Anyone can verify a receipt, offline, without an account and without trusting us.
Website: pcrzero.com
Sign up / API keys: pcrzero.com/signup
API: api.pcrzero.com
Add the server to your MCP client. The package runs over stdio — your agent host launches it; nothing listens on a port.
Claude Code
claude mcp add pcrzero -e PCRZERO_API_KEY=<your-key> -- npx -y @scytalex-llc/pcrzero-mcpClaude Desktop / any JSON-configured MCP client
{
"mcpServers": {
"PCRZERO": {
"command": "npx",
"args": ["-y", "@scytalex-llc/pcrzero-mcp"],
"env": { "PCRZERO_API_KEY": "<your-key>" }
}
}
}No key yet? Leave env out. verify_receipt and get_keyset work with no API key
and no account — only the paid tool needs one.
Requires Node 22 or later.
Related MCP server: agent-receipts-mcp
Tool | Cost | What it does |
| Metered — bills one | Adjudicates an attestation document against a policy on the live API and returns the verdict with a signed receipt pair. A |
| Free, and it stays free | Checks a PCRZERO receipt pair against the signing keyset: whether the signature holds, and whether the receipt says what it appears to say. Offline by default — supply |
| Free | Returns the current PCRZERO signing keyset — key ids, public halves, each key’s status. Public and unauthenticated. The same document an outside party fetches to check a receipt without trusting us. |
Current pricing is published at pcrzero.com — it is deliberately not baked into this README or into any tool description.
PCRZERO_API_KEY in the server’s environment, via your MCP client configuration. It is
sent as Authorization: Bearer on issue_receipt calls and used nowhere else: the key
never appears in tool results, error text, or logs — not even redacted. With no key
configured, issue_receipt refuses cleanly (auth_missing) and the two free tools keep
working.
API errors pass through verbatim (code, message, request_id). This server never
rewrites, retries, or softens a billing refusal.
A PCRZERO receipt is checkable by anyone holding the public keyset — including people
who are not our customers and never will be. Call get_keyset once (or fetch
https://api.pcrzero.com/v1/keys yourself), pin it, and verify_receipt runs entirely
offline from then on. If we disappeared tomorrow, every receipt ever issued would still
verify.
stdio only. No listen socket, no state, no receipt storage, no key-management tools — key management is a human path at pcrzero.com by design.
Proprietary — © Scytalex LLC. The receipt verification path is free to use for anyone, forever.
This server cannot be deployed
Issue & verify signed (ed25519), hash-chained, timestamped provenance receipts for agent actions.
Post-quantum, tamper-evident receipts for agent actions. Ed25519 + ML-DSA-65, offline verify.
Policy gate and signed trust receipts for autonomous agent actions.
Deterministic authorization for one proposed AI agent action, returned with a signed receipt.