Fabric Verify

Fabric Verify MCP server

Give your AI agent a tamper-evident record of what it did.

Each time the agent records an action, this server signs a short record on your machine, with the agent's own key, and adds it to the Fabric Verify public log. Later you get a proof that anyone can check offline, without trusting you or us.

A proof shows that this exact record existed, unchanged, by a certain time. It does not show that what the record describes is true.

Your text stays with you. Each record sends a salted fingerprint of it, plus the signature. The public log permanently shows the agent name, key name, action kind, time and public key with every record, so never put personal data in FABRIC_AGENT or FABRIC_KID.

Price

Tool	Cost
record_action	$0.005 per record, from prepaid credit
get_proof, check_balance, buy_credit_link	free

Buy credit by card at https://augmentev.com/pricing#buy. Your credit key (fvk_…) is shown once after payment, so save it in a password manager.

Install

You need Node.js 20 or later. Add this to your MCP client's configuration:

{
  "mcpServers": {
    "fabric-verify": {
      "command": "npx",
      "args": ["-y", "@augmentev/fabric-verify-mcp"],
      "env": {
        "FABRIC_CREDIT_KEY": "fvk_...",
        "FABRIC_AGENT": "my-agent"
      }
    }
  }
}

In Claude Code:

claude mcp add fabric-verify --env FABRIC_CREDIT_KEY=fvk_... --env FABRIC_AGENT=my-agent -- npx -y @augmentev/fabric-verify-mcp

Settings

Variable	Default	Meaning
FABRIC_CREDIT_KEY	(required)	Your credit key. Keep it secret.
FABRIC_AGENT	mcp-agent	A stable name for this agent (printable ASCII, no spaces).
FABRIC_KID	<agent>-key-1	A name for the agent's signing key. Change it when you rotate the key.
FABRIC_HOME	~/.fabric-verify	Where the agent key and your records are kept (private to your user).
FABRIC_MAX_SPEND_USD	1	The most this server may spend in one session.

Tools

• record_action (kind, summary, optional idempotency_key): signs and logs one record, then returns its log index. The summary and its salt are saved under FABRIC_HOME/records/<api host>/<index>/, so you can later show what the record was about. If a call fails, call again with the same idempotency_key, kind and summary: the exact same signed record is resent and charged at most once.
• get_proof (index, optional wait_seconds up to 45): fetches the proof and saves it next to the record. Proofs are usually ready a few minutes after recording.
• check_balance: shows your remaining credit and this session's spend.
• buy_credit_link (amount_usd: 25, 50, 100 or 500): returns a card checkout link for a person to open. This tool charges nothing.

Check a proof

Download the verifier and the published log keys from https://augmentev.com/verify, then run this in the record's folder:

augmentev-verify log-proof proof.json --pins fabric-log-v1.json --audit agent-record.json

Pin the version

For production agents, pin an exact version, such as npx -y @augmentev/[email protected], and update deliberately. The package ships a lockfile (npm-shrinkwrap.json) so its dependencies are fixed too.

Keep your agent key

The agent key is FABRIC_HOME/agent-ed25519.pem. Back it up. Each key name (FABRIC_KID) belongs to one key for good. If you lose the key, set a new FABRIC_KID.

Support

[email protected]

Licence

Apache-2.0. "Fabric Verify" and "AugmentEV" are trademarks of AugmentEV Inc.; the licence grants no rights to them.