@treeship/mcp -- Treeship

Install

npm install @treeship/mcp

Usage

One import change. Zero other code changes.

// Before (no attestation):
import { Client } from '@modelcontextprotocol/sdk';

// After (every tool call attested):
import { Client } from '@treeship/mcp';

Everything else stays the same. The wrapped Client class extends the original MCP Client and re-exports all other symbols unchanged.

import { Client } from '@treeship/mcp';

const client = new Client(
  { name: 'my-agent', version: '1.0' },
  { capabilities: {} },
);
await client.connect(transport);

const result = await client.callTool({
  name: 'search',
  arguments: { q: 'treeship' },
});

// Result now carries attestation metadata:
// result._treeship = { intent: "art_xxx", tool: "search", actor: "agent://mcp-my-agent" }

What gets attested

For every callTool() invocation, the bridge produces two attestations:

Intent (before the call, awaited) -- proves what was about to happen. The tool name and a SHA-256 digest of the arguments are recorded.
Receipt (after the call, fire-and-forget) -- proves what came back. Records elapsed time, exit status, and a digest of the output. The receipt is never awaited, so it never blocks the response.

Arguments and results are never stored directly. Only their SHA-256 digests enter the artifact. The digest proves which data was involved without exposing the data itself.

If attestation fails for any reason (CLI not installed, network issue, signing error), the tool call still completes normally. Treeship never breaks your MCP workflow.

Result metadata

When attestation succeeds, the result object includes a _treeship field:

interface ToolReceipt {
  intent: string;   // artifact ID of the intent attestation
  tool: string;     // tool name, e.g. "search"
  actor: string;    // actor URI used for both attestations
}

Environment variables

Variable	Effect
`TREESHIP_DISABLE=1`	Disable all attestation. Pure passthrough to the upstream MCP client.
`TREESHIP_ACTOR`	Override the default actor URI (default: `agent://mcp-{clientName}`)
`TREESHIP_APPROVAL_NONCE`	Attach an approval nonce to intent attestations
`TREESHIP_DEBUG=1`	Log all attestation activity to stderr

Actor naming

By default, the actor URI is derived from the name field in your Implementation object:

new Client({ name: 'my-agent', version: '1.0' }, { capabilities: {} });
// Default actor: agent://mcp-my-agent

Override it with the TREESHIP_ACTOR environment variable when you need a specific identity.

To attest that a human approved a tool call before it happened, set the TREESHIP_APPROVAL_NONCE environment variable. The nonce is included in the intent attestation and links back to the approval artifact.

export TREESHIP_APPROVAL_NONCE=abc123

This is useful when a human reviews and approves a planned action before the agent executes it.

@treeship/mcp