@signet-auth/mcp-server

Execution-boundary verification for MCP servers. Reject unsigned, tampered, stale, replayed, or mis-targeted requests before tool execution, and optionally co-sign responses.

Best for:

• MCP server owners who want verification before execution
• Enforcing freshness, target binding, and tool/params matching
• Adding replay protection and response co-signing at the server boundary

Use another package if:

• You control the MCP client transport and need outbound signing: @signet-auth/mcp
• You want Signet as a standalone MCP server instead of an in-process library: @signet-auth/mcp-tools

Install

npm install @modelcontextprotocol/sdk @signet-auth/mcp-server

Usage

import { CallToolRequestSchema } from "@modelcontextprotocol/sdk/types.js";
import { FileNonceCache, verifyRequest } from "@signet-auth/mcp-server";

const nonceCache = new FileNonceCache(".signet/nonces.json");

server.setRequestHandler(CallToolRequestSchema, async (request) => {
  const verified = verifyRequest(request, {
    trustedKeys: ["ed25519:..."],
    expectedTarget: "mcp://my-server",
    maxAge: 300,
    nonceCache,
  });

  if (!verified.ok) {
    return {
      content: [{ type: "text", text: verified.error ?? "verification failed" }],
      isError: true,
    };
  }
  if (!verified.trusted) {
    return {
      content: [{ type: "text", text: "untrusted signer" }],
      isError: true,
    };
  }

  // process tool call...
});

Useful exports:

• verifyRequest() checks signature validity, freshness, target binding, and tool/params matching, and tells you whether the signer is trusted
• FileNonceCache adds replay protection that survives ordinary restarts in a single-host pilot deployment
• NonceCache is still available for tests and demos
• signResponse() lets the server co-sign a response after a successful trusted verifyRequest(), by default records an executed or failed outcome, and also accepts an explicit outcome override for cases like rejected or requires_approval

Related packages

• @signet-auth/mcp — sign outbound MCP requests on the client side
• @signet-auth/core — lower-level cryptographic primitives
• @signet-auth/mcp-tools — standalone MCP server exposing Signet tools
• Full documentation & all SDKs

If Signet is useful to you, star us on GitHub — it helps others discover the project.