# 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. **Action details stay private. The public log holds only a salted fingerprint, the action kind and time, and coded identifiers that only you, or an auditor you give an audit pack to, can link to your agents.** You cannot edit or delete a record once it is logged. Records made before 9 November 2026 were in an earlier log that we retired and can no longer be fetched. AugmentEV keeps the agent name, key name and public key in an erasable store so they can go into your audit packs, so never put personal data in `FABRIC_AGENT` or `FABRIC_KID`.

## Price

| Tool | Cost |
|---|---|
| `record_action`, `record_event` | $0.005 per record, from prepaid credit |
| `get_proof`, `check_balance`, `buy_credit_link`, `export_events` | 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:

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

In Claude Code:

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

## Remote connector

The Cursor plugin (`.cursor-plugin/plugin.json` and `mcp.json`) and the Gemini CLI extension (`gemini-extension.json`) in this repository don't run this package. They connect to the hosted server at `https://mcp.augmentev.com/mcp`, the address chat apps use as a custom connector. There is nothing to install.

When an app connects, it sends you to a sign-in page where you enter your credit key, a name for the assistant and a daily spending limit ($0.50 to $20). The app gets an access token, not your key.

The remote connector has four tools: `record_action`, `record_event`, `get_proof` and `check_balance`. Records made through it are signed by a key AugmentEV hosts for your account and are labelled "augmentev-hosted"; only this connector can make records with that label. For records signed by a key only your agent holds, use the package above.

## 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`, optional `approval_record`): 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.
- **`record_event`** (`event`, `body`, optional `action`, `run_id`, `step_id`, `parent_record`, `delegation_record`, `kind`, `idempotency_key`): signs and logs one structured agent event: a tool call, its result, an approval, a delegation, a policy decision, a halt and so on (format `augmentev/fabric-agent-event/v1`). Same price as `record_action`. The event is the record's payload and stays on this machine. It returns `record`, which later events link to. For a tool call, pass `action` (tool, server, arguments), and pass the same `action` when recording its approval, so both name the same action. If your account's governance policy requires approval for tool calls, set `body.approval_record` and the approval is presented to the log, which uses it once. A tool result is signed as kind `other`, so that rule does not also gate results.
- **`export_events`** (`run_id` or `indices`): bundles events recorded from this machine, with their proofs, into one file that anyone can check offline with `augmentev-verify agent-events`. Free. Fetch the proofs first. The bundle shows that its events were logged unchanged and that every link points to an earlier event of the right type. It does not show that the bundle holds every event, or that a described tool result is true. Events recorded on another machine (another agent's approval, say) are in that machine's bundle; merge records in log order to check them together.
- **`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:

```bash
augmentev-verify log-proof proof.json --pins fabric-log-v2.json --audit agent-record.json
```

## Pin the version

For production agents, pin an exact version, such as `npx -y @augmentev/fabric-verify-mcp@0.2.2`, 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

support@augmentev.com

## Licence

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