Verify a SCITT receipt from a Forestrie transparency log under a trust root you hold. Offline: no backend, no account, no key, no network. An MCP server whose only tools verify and decode receipts.

{
  "mcpServers": {
    "forestrie-verify": {
      "command": "npx",
      "args": ["-y", "@forestrie/mcp-verify"]
    }
  }
}

npx -y @forestrie/mcp-verify demo

Why

Agents act on statements they did not witness being made: a quote, an approval, a tool result, another agent's output. Usually the record of what was said is kept by the party that said it, so nobody downstream can ask "did you really say that, and did you say it to everyone?"

A Forestrie receipt is a proof that a statement was sealed into an append-only transparency log. This package checks that proof against a trust root you hold, in your own process, without contacting Forestrie. With the right root it also answers the harder question: whether the log you were shown is the log everyone else was shown. What transparency adds, where it stops, and what a receipt contains: TRANSPARENCY.md.

What it proves

Tool	Reference verb	What it answers
`verify_receipt`	`forestrie verify`	Were these exact payload bytes sequenced at this entry id?
`verify_grant_receipt`	`forestrie verify-grant`	Was this grant admitted to this log — i.e. was the signer entitled to write?
`verify_self`	`forestrie verify`	Does this package's own release receipt vouch for the bytes it ships?
`decode_receipt`	`forestrie decode-receipt --json`	What is actually in this receipt? (Renders the CBOR only. Verifies nothing.)

Every tool is annotated readOnlyHint: true, openWorldHint: false. That is not decoration: it is the machine-readable form of "this tool touches nothing", and an agent can see it without running anything.

Trust roots

You do not ask for "verification". You say which root you trust, and the result says what that root can see:

Root	What you supply
`genesis`	the forest's genesis document, captured when you registered
`known-log-key`	a log owner key you hold out of band
`known-accumulator`	a snapshot of the log's peaks, from a chain read
`checkpoint-chain`	a retained chain of `.sth` checkpoints

The roots are not ordered by strength. The first two check the operator's signature locally and cannot see a split view. The last two match the peak against an accumulator the operator does not control, and can. Every result answers four questions, sealing, split-view, append-authority and attribution, each ok, failed, or not_answered_by_this_root. The last is a real answer and must reach the user; a client that renders only ok is using this tool wrong.

When each root is the effective choice, why a genesis document fetched at check time is weaker than one kept from registration, what a signature root cannot distinguish, and the demo transcript: docs/trust-roots.md.

Not a trust circle

The root of trust is the univocity checkpoint the receipt chains to, not the package; the package supplies the arithmetic, which any independent implementation can re-run.

Which is why this repo goes to some trouble to make that re-running possible:

Frozen conformance vectors, sha256-pinned to their manifest, shipped inside the tarball. See fixtures/PROVENANCE.md.
files includes src. The package that asks you to trust its arithmetic ships the arithmetic.
Exact, provenance-attested dependencies — no bundling, so npm ls and npm audit signatures both see the real graph. Bundling would hide @forestrie/receipt-verify's own SLSA attestation behind ours.

The verification itself is @forestrie/receipt-verify, pinned to an exact version, published, MIT, and SLSA-attested independently of this package. decode_receipt's rendering stays a local implementation — over the same published packages, against the same public label registry — rather than a dependency on @forestrie/forestrie-cli, whose published decoder is otherwise a drop-in. Delegating to it has been tried twice and reverted twice: the two label tables still name some codepoints with different text, and that text is output the tool prints, so adopting it is a deliberate change to what you see rather than a dependency bump. See AGENTS.md.

Installing the package pulls in more than a verifier needs. @modelcontextprotocol/sdk brings a web stack, including express, hono, jose, cors and ajv, for HTTP transports this package never uses: it constructs only the stdio transport. The verification core never imports the SDK, and the browser-safety gate enforces that, so importing the package's "." export gives you the arithmetic without any of it.

At release time, this package also registers its own provenance in a Forestrie log and ships the receipt inside the tarball — two independent trust roots, npm's SLSA provenance and a Forestrie receipt, rather than one circular one. See docs/self-registration.md.

That bundle is also the subject of a worked example: fetching this package's own release receipt from the public lane, verifying it under the bundled key, seeing the documented delegation_invalid under the genesis root, and getting split-view ok from a chain read — end to end in a few seconds, with no account. It lives in @forestrie/mcp-resolve's README, because fetching is that package's job, not this one's.

Bundled resources, and the two calls they make runnable

The tarball ships its fixtures as forestrie://fixtures/… MCP resources, so an agent that holds nothing of its own can run a real verification. Two calls reach a pass from resources alone; both are asserted by test/node/mcp-smoke.test.ts.

A grant receipt at the genesis root — verify_grant_receipt with:

Argument	Resource
`receipt`	`golden/grant-receipt.cbor`
`committedGrant`	`golden/committed-grant.cbor` (derived from `golden/manifest.json` at read time)
`entryId`	the text of `golden/entry-id.txt`
`trust`	`{root: "genesis", genesis: golden/grant-genesis.cbor}`

Result: verify-grant: PASS · root=genesis · sealing ok, split-view not answered at this root, append-authority ok, attribution ok.

A payload receipt at an accumulator root, offline, against a real anchor — verify_receipt with the lane-A bundle (fixtures/lane-a/PROVENANCE.md): a real receipt from a public lane and the accumulator the univocity contract had published for its log at block 46770471, captured by an independent chain read. (That lane's content was reset on 2026-09-20; the bytes still verify, the URLs they came from no longer resolve.)

Argument	Resource
`receipt`	`lane-a/receipt.cbor`
`payload`	`lane-a/statement.cose`
`entryId`	the text of `lane-a/entry-id.txt`
`trust`	`{root: "known-accumulator", accumulator: lane-a/accumulator.cbor}`

Result: verify: PASS · root=known-accumulator · sealing ok, split-view ok, append-authority ok, attribution ok, with anchor.matchedPeak set. Unlike the demo's self-derived snapshot, this anchor is the contract's published state, so the split-view answer is evidence as of that block. The same receipt passes under {root: "known-log-key", keyXy: {b64: <text of lane-a/log-key.xy.b64>}} and reports delegation_invalid under {root: "genesis", genesis: lane-a/genesis.cbor}, because its log is a grandchild of the forest root (docs/self-registration.md).

A resource's bytes are passed back as {b64: <the blob>}; a text resource such as lane-a/log-key.xy.b64 is base64 text already, so its text goes in b64 as is. golden/burial/public-key.xy.b64 offers the burial chain's root key the same way, so checkpoint-chain can be driven from resources — to its documented negative verdict, since the burial bundle ships no leaf preimage.

Registry

This server is listed as dev.forestrie/verify in the official MCP registry.

Development

mise install           # node 22.14.0, pnpm 10.6.5
pnpm install
pnpm test              # browser-safe gate + encoding-copy gate + server.json gate + unit tests
pnpm build

Conventions, invariants and the release checklist: AGENTS.md.