Alter Identity MCP Server

@truealter/sdk

~Alter Identity SDK - query the continuous identity field from any JavaScript/TypeScript environment.

Install: npm install @truealter/sdk

A thin client over the ~Alter MCP server (Streamable HTTP, JSON-RPC 2.0, MCP spec 2025-11-25) with x402 micropayment support, ES256 provenance verification, and config generators for Claude Code, Cursor, and generic MCP clients.

• Branded host: https://mcp.truealter.com (serves .well-known/mcp.json for discovery)
• JSON-RPC wire endpoint: https://mcp.truealter.com/api/v1/mcp - this is what Streamable HTTP POSTs target (the SDK default)
• Wire protocol: Streamable HTTP, JSON-RPC 2.0, MCP 2025-11-25 (server negotiates 2025-06-18 + 2025-03-26 for backwards-compatible clients)
• Tools: 37 publicly advertised, 28 free (L0) + 9 premium (L1-L5), kept in sync with ~Alter's live MCP server at every publish.
• Runtime: Node 18+, Deno, Bun, Cloudflare Workers, modern browsers
• Crypto: @noble/ed25519 + @noble/hashes (no other dependencies)
• Bundle: ESM + CJS dual output

Quickstart

npm install @truealter/sdk

Then import the client in your code (see the API section below). The day-to-day command line lives in @truealter/cli:

alter init
alter verify ~alter

Bridge vs SDK

This package ships a stdio bridge entrypoint (bin/mcp-bridge.ts, built to dist/bin/mcp-bridge.js) that the alter CLI launches by file path via its mcp-bridge subcommand. It is a dev/demo surface for dropping ~Alter into MCP hosts that speak the stdio transport (Claude Code, Cursor, Continue, Windsurf). It is useful for handshake, tools/list, and L0 tool calls, but it does not carry ES256 per-invocation signing: authenticated MCP tools will fail at the server edge when reached through the bridge. For production use, import @truealter/sdk directly and construct an MCPClient / AlterClient with the optional signing parameter; that path is the primary one and carries the provenance envelope end-to-end. Bridge signing is planned for a future release.

CLI

This package exposes no command-line binary of its own: it is a library you import. The bridge entrypoint above is not a published bin; it is resolved by file path from the alter CLI, which is distributed separately as @truealter/cli. Run alter --help for the inline reference.

Why ~Alter is not IAM

Identity Access Management answers who is logged in. ~Alter answers who they actually are - a continuous field of recognition that any IAM stack can sit on top of.

Theoretical Foundation

~Alter is the working instantiation of an eight-paper academic corpus on identity field theory. The SDK below is what happens when the theory ships as protocol. Each paper is open access on figshare under CC-BY 4.0.

For the lay-register chapter version, see /origin.

API

Initialise the client

import { AlterClient, X402Client } from "@truealter/sdk";

const alter = new AlterClient({
  endpoint: "https://mcp.truealter.com/api/v1/mcp", // optional - this is the default; bare host returns 405
  x402: new X402Client({                  // optional - only required for premium tools
    signer: yourViemOrEthersSigner,
    maxPerQuery: "0.10",
  }),
});

Authentication. The client above is anonymous, and every free L0 tool answers with no credential. For tools that act on your own identity (standing requirements, the Golden Thread, member self-writes), run alter login once: it provisions your member credential into the local session (~/.config/alter/session.json). The hosted endpoint is bearer-first, so the @truealter/cli bridge reads that session credential for you; you never mint or paste a key. If you construct a client yourself, pass that same session credential as the optional apiKey option.

Minimum-version preflight (required)

~Alter's backend publishes a per-client minimum-version floor. The SDK preflights this floor lazily on the first network call: no explicit call is required for the common case. If the running SDK is below the floor for alter-identity, the SDK throws BelowFloorError with the upgrade command attached.

The floor document is signed by the backend with a floor-only Ed25519 private key. The SDK ships only the corresponding public keys (KNOWN_FLOOR_PUBLIC_KEYS, a key_id to SPKI-PEM map): no signing secret ships in the client, and a compromised client cannot forge floor documents. The key_id is the first 8 hex chars of SHA-256 of the raw 32-byte Ed25519 public key, so clients select the right key during a rotation. An unknown key_id or an invalid signature is treated as a cache miss (refetch), never as a pass.

import { AlterClient, BelowFloorError, checkMinVersion } from "@truealter/sdk";

// Optional: run the preflight explicitly to surface the upgrade
// prompt at startup, before any real work happens:
try {
  await checkMinVersion();
} catch (err) {
  if (err instanceof BelowFloorError) {
    console.error(`upgrade required: ${err.upgrade_cmd}`);
    process.exit(1);
  }
  throw err;
}

// The constructor installs the same hook lazily: it fires on your
// first request automatically:
const alter = new AlterClient();
try {
  await alter.verify("~alter");
} catch (err) {
  if (err instanceof BelowFloorError) {
    // Re-thrown on every subsequent call until you upgrade.
    console.error(`upgrade: ${err.upgrade_cmd}`);
  }
}

BelowFloorError carries the canonical envelope fields as enumerable properties so consumers can branch without re-parsing:

Opt-out (discouraged). Pass unsafe_skipVersionCheck: true to skip the client-side preflight. The server-side floor gate still rejects below-floor clients with HTTP 426 regardless: disabling the SDK-side preflight only swaps a clean typed error for an opaque network failure on every subsequent call.

const alter = new AlterClient({ unsafe_skipVersionCheck: true });

Worked example: see examples/min-version-check/.

Identity headers

Every outbound request from AlterClient / MCPClient carries three identity headers that the server-side floor middleware consults:

These are MANDATORY on every authenticated backend endpoint so the server can enforce its minimum supported client version. The User-Agent header remains informational and is NEVER used for floor enforcement.

Free tier (L0 - no payment required)

// Verify a registered identity by handle, email, or id
const verified = await alter.verify("~alter");
const verifiedById = await alter.verify(
  "550e8400-e29b-41d4-a716-446655440000",
  {
    archetype: "weaver",
    min_engagement_level: 3,
    traits: { pressure_response: { min: 0.6 } },
  },
);

// Reference data - the 12 ~Alter archetypes
const archetypes = await alter.listArchetypes();

// Identity depth and available tool tiers
const depth = await alter.getEngagementLevel({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

// Search by trait criteria - no PII exposed, max 5 results
const matches = await alter.searchIdentities({
  trait_criteria: {
    pressure_response: { min: 0.7 },
    cognitive_flexibility: { min: 0.6 },
  },
});

// Golden Thread program status
const thread = await alter.goldenThreadStatus();

Premium tier (L1-L5 - x402 payment required)

// L1 - Extract trait signals from text ($0.01, first 100 free per bot)
const signals = await alter.assessTraits({
  text: "I led the incident response when our payment rails went down...",
  context: "interview transcript",
});

// L2 - Full 33-trait vector ($0.10)
const vector = await alter.getFullTraitVector({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

// L4 - Belonging probability for a person-job pairing ($0.60)
const belonging = await alter.computeBelonging({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
  job_id: "f47ac10b-58cc-4372-a567-0e02b2c3d479",
});

// L5 - Top match recommendations ($1.00)
const recommendations = await alter.getMatchRecommendations({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
  limit: 5,
});

// L5 - Human-readable narrative explaining a match ($1.00)
const narrative = await alter.generateMatchNarrative({
  match_id: "9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d",
});

Provenance verification

// Every medium- and high-sensitivity response is signed with ES256.
// Verification is opt-in - call alter.verifyProvenance(...) yourself.
const result = await alter.getFullTraitVector({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

const check = await alter.verifyProvenance(result._meta?.provenance);
if (!check.valid) throw new Error(`provenance failed: ${check.reason}`);

// Verify that schema hashes published in tools/list._meta.signatures
// match the local representation of each tool.
const tools = await alter.mcp.listTools();
const sigs = tools._meta?.signatures ?? {};
const results = await alter.verifyToolSignatures(tools.tools, sigs);
const tampered = results.filter((r) => !r.valid);
if (tampered.length) throw new Error(`tampered tools: ${tampered.map((t) => t.tool).join(", ")}`);

Discovery

import { discover } from "@truealter/sdk";

// Three-step discovery cascade: DNS TXT to mcp.json to alter.json
const descriptor = await discover("truealter.com");
// returns { url: "https://mcp.truealter.com/api/v1/mcp", transport, source, publicKey, x402Contract, capability }

Low-level MCPClient

import { MCPClient } from "@truealter/sdk";

const mcp = new MCPClient({ endpoint: "https://mcp.truealter.com/api/v1/mcp" });
await mcp.initialize();
const tools = await mcp.listTools();
const response = await mcp.callTool("verify_identity", {
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

MCP Config Generation

The SDK ships config generators for the major MCP-aware clients. Each emits a JSON snippet you can paste (or write directly) into the appropriate file.

Claude Code (.mcp.json)

import { generateClaudeConfig } from "@truealter/sdk";
import { writeFileSync } from "node:fs";

const config = generateClaudeConfig({
  endpoint: "https://mcp.truealter.com/api/v1/mcp",
});

writeFileSync(".mcp.json", JSON.stringify(config, null, 2));

Resulting .mcp.json:

{
  "mcpServers": {
    "alter": {
      "url": "https://mcp.truealter.com/api/v1/mcp",
      "transport": "streamable-http",
      "description": "~Alter Identity - psychometric identity field for AI agents"
    }
  }
}

This config reaches every free L0 tool anonymously. For authenticated access, run alter login and let the CLI write the config (alter config); the bearer-first bridge then carries your session credential, so no key sits in the file.

Cursor (.cursor/mcp.json)

import { generateCursorConfig } from "@truealter/sdk";
import { writeFileSync } from "node:fs";

const config = generateCursorConfig({
  endpoint: "https://mcp.truealter.com/api/v1/mcp",
});

writeFileSync(".cursor/mcp.json", JSON.stringify(config, null, 2));

Generic MCP client

import { generateGenericMcpConfig } from "@truealter/sdk";

const config = generateGenericMcpConfig({
  endpoint: "https://mcp.truealter.com/api/v1/mcp",
  serverName: "alter", // editor-specific key under mcpServers
});

CLI

The command line lives in @truealter/cli, not in this SDK package:

alter init                 # generate keypair, discover MCP, write ~/.config/alter/identity.json
alter config               # print Claude .mcp.json snippet (default)
alter config --cursor      # print Cursor .cursor/mcp.json snippet
alter config --generic     # print generic mcpServers snippet
alter verify ~alter        # verify an identity
alter status               # show connection state and probe the endpoint

x402 Micropayments

~Alter monetises premium tools via the x402 standard - HTTP 402 Payment Required with on-chain settlement.

The retry flow

1. Client calls a premium tool without a payment header.
2. Server replies 402 Payment Required with a payment requirement (amount, recipient, asset, network).
3. Client signs and broadcasts a USDC transfer on Base L2, attaches the proof, retries.
4. Server validates the proof, executes the tool, signs the response with ES256, returns it.
5. AlterRouter executes the split on-chain in the same transaction. The data subject receives Identity Income directly; ~Alter receives only its protocol cut. No custodian, no broker.

The SDK handles steps 2-4 automatically when an X402Client with a configured signer is passed in.

Tier structure

x402 micropayments at L0-L5 trust tiers. Per-call pricing visible after alter login.

Identity income split

The majority of every settled call flows to the data subject as Identity Income. Split details available post-authentication via alter status.

Code example

import { AlterClient, X402Client, type X402Signer } from "@truealter/sdk";

// Bring your own signer - viem, ethers, a hardware wallet bridge, anything.
// The SDK ships without a wallet dependency on purpose.
const signer: X402Signer = {
  async settle(envelope) {
    const txHash = await yourWallet.sendUsdcTransfer({
      to: envelope.recipient,
      amount: envelope.amount,
      chain: envelope.network,
    });
    return {
      reference: txHash,
      network: envelope.network,
      amount: envelope.amount,
      asset: envelope.asset,
    };
  },
};

const alter = new AlterClient({
  endpoint: "https://mcp.truealter.com/api/v1/mcp",
  x402: new X402Client({
    signer,
    networks: ["base", "base-sepolia"], // policy allow-list
    assets: ["USDC"],
    maxPerQuery: "0.10",                 // refuse anything over $0.10 USDC
  }),
});

// Auto-retries with payment when the server returns 402
const vector = await alter.getFullTraitVector({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

If a quoted envelope exceeds maxPerQuery, uses an unallowed network, or names an unallowed asset, the SDK rejects the call with AlterError before invoking the signer - no on-chain transaction is broadcast.

Provenance Verification

Every response from a medium- or high-sensitivity tool ships with an ES256 JWS in _meta.provenance. The signature covers a canonical JSON serialisation of the response payload, the tool name, the call timestamp, the requesting agent's key hash, and a monotonic sequence number.

const result = await alter.getFullTraitVector({
  member_id: "550e8400-e29b-41d4-a716-446655440000",
});

const check = await alter.verifyProvenance(result._meta?.provenance);
if (!check.valid) throw new Error(`~alter provenance check failed: ${check.reason}`);

The SDK fetches public keys from https://api.truealter.com/.well-known/alter-keys.json and caches them per their Cache-Control headers. The endpoint returns a JWKS containing all current and recently-rotated signing keys; verifying clients should accept any key whose kid matches and is still within its validity window.

verify_at hostname allowlist (v0.1.1+)

Every provenance envelope may carry a verify_at hint telling the SDK where to fetch the JWKS from. Because that hint is server-supplied, a hostile MCP server could otherwise point it at an attacker-controlled JWKS and pass ES256 verification with its own signing key. The SDK therefore gates verify_at through a hostname allowlist (default: api.truealter.com, mcp.truealter.com) and rejects http:// URLs unconditionally. Downstream integrators with their own deployment can extend the allowlist - without forking the SDK - via verifyAtAllowlist on either AlterClient or a direct verifyProvenance() call:

import { AlterClient, DEFAULT_VERIFY_AT_ALLOWLIST } from "@truealter/sdk";

const alter = new AlterClient({
  verifyAtAllowlist: [
    ...DEFAULT_VERIFY_AT_ALLOWLIST,   // keep the ~Alter canonicals
    "keys.myorg.example",              // plus your own JWKS host
  ],
});

If you pin jwksUrl explicitly, the envelope's verify_at is ignored entirely - the pinned URL wins. The https: scheme requirement applies to pinned URLs too.

Why this matters

Provenance verification is how Agent A trusts that data from Agent B truly came from ~Alter. If Agent B forwards a trait vector or belonging score, Agent A can replay the JWS against ~Alter's published keys and confirm - without contacting ~Alter again - that the payload is authentic, untampered, and was issued for the person Agent B claims it concerns. No shared secret, no trust in the intermediary, no out-of-band coordination.

This is what makes ~alter usable as identity infrastructure rather than just an API: signed claims propagate across agent networks the same way DKIM-signed mail propagates across SMTP relays.

Discovery

~Alter follows the discovery cascade specified in draft-morrison-mcp-dns-discovery-01. Given a domain (e.g. truealter.com), the SDK resolves the MCP endpoint in three steps, falling through on each failure:

1. DNS TXT - query _mcp.truealter.com for a TXT record of the form mcp=https://mcp.truealter.com;version=2025-11-25. This is the fastest path and works without an HTTP round-trip.
2. .well-known/mcp.json - fetch https://truealter.com/.well-known/mcp.json for the standard MCP server descriptor. This is the cross-vendor fallback.
3. .well-known/alter.json - fetch https://truealter.com/.well-known/alter.json for the ~Alter-specific descriptor, including signing keys, x402 wallet address, supported tool tiers, and federation endpoints.

import { discover } from "@truealter/sdk";

// Cascading discovery (DNS TXT to mcp.json to alter.json)
const descriptor = await discover("truealter.com");

// Skip the DNS step (e.g. in browsers or Cloudflare Workers)
const httpsOnly = await discover("truealter.com", { skipDns: true });

This draft is the author's Internet-Draft (not yet adopted by an IETF working group); until adoption, the cascade order may change. Pin the SDK version to a specific minor release if you depend on this behaviour.

Tools

Free tools (L0 - no payment required)

Premium tools (L1-L5 - x402 payment required)

Member self-write tools (submit_context, submit_batch_context, submit_structured_profile, submit_social_links) are live but member-self-scoped: a member calls them on their own identity with an authenticated member credential (alter login). They are not anonymously discoverable, so they do not appear in the advertised tool list above.

Contributing

Bug reports and small patches are welcome - see CONTRIBUTING.md.

Security

Report vulnerabilities to security@truealter.com - see SECURITY.md for scope and the coordinated disclosure policy. Please do not open public issues for security bugs.

License

Apache License 2.0. See LICENSE for the full text.

Copyright 2026 Alter Meridian Pty Ltd (ABN 54 696 662 049).