Neo N3 MCP Server

Neo N3 MCP Server

@r3e/neo-n3-mcp is an MCP server for Neo N3 blockchain queries and controlled, auditable transaction submission. It ships three entrypoints:

Entrypoint	Command	Protocol
MCP stdio	npm start	MCP over stdin/stdout, for local clients such as Claude Desktop and Cursor
MCP Streamable HTTP	npm run start:mcp-http	MCP over HTTP, for remote MCP clients
REST API	npm run start:http	Bespoke REST/JSON; not an MCP transport

The two HTTP servers are unrelated and configured separately. See Remote MCP over Streamable HTTP and docs/remote-mcp-transport.md.

Current version: 3.1.0. Node.js >=22 is required.

Quick Start

Install and run the MCP stdio server:

npm install -g @r3e/neo-n3-mcp
neo-n3-mcp

Or run it without a global install:

npx -y @r3e/neo-n3-mcp

Example Claude Desktop or Cursor configuration:

{
  "mcpServers": {
    "neo-n3": {
      "command": "npx",
      "args": ["-y", "@r3e/neo-n3-mcp"],
      "env": {
        "NEO_NETWORK": "testnet",
        "NEO_TESTNET_RPC": "https://testnet1.neo.coz.io:443",
        "LOG_LEVEL": "info"
      }
    }
  }
}

Programmatic API

The package root exports the MCP server, HTTP server, services, network enums, and validated configuration:

import { NeoNetwork, NeoService } from '@r3e/neo-n3-mcp';

const neo = new NeoService(
  'https://testnet1.neo.coz.io:443',
  NeoNetwork.TESTNET,
);

const blockCount = await neo.getBlockCount();
console.log({ blockCount, height: Math.max(0, blockCount - 1) });

NeoN3McpServer exposes run() and close() for applications that manage the stdio transport lifecycle themselves.

Configuration

Variable	Purpose	Default
NEO_NETWORK	mainnet, testnet, or both; HTTP requires one network	both
NEO_MAINNET_RPC	Mainnet RPC endpoint	https://mainnet1.neo.coz.io:443
NEO_TESTNET_RPC	Testnet RPC endpoint	https://testnet1.neo.coz.io:443
NEO_RPC_TIMEOUT_MS	Per-operation Neo RPC deadline in milliseconds	15000
NEO_ALLOW_INSECURE_RPC	Allow a remote plaintext HTTP RPC URL	false
NEO_MAX_TRANSACTION_FEE_GAS	Maximum combined system and network fee for a signed transaction, in GAS	20
NEO_ENABLE_WRITES	Register state-changing tools and HTTP routes	false
NEO_SIGNER_WIF_FILE	Owner-only regular file containing the single server signer WIF	required for writes
NEO_WRITE_STATE_DIR	Durable idempotency journal directory	$WALLETS_DIR/.write-operations
HTTP_WRITE_APPROVAL_API_KEY	Independent bearer token for HTTP write approval	required for writes
NEO_ENABLE_WALLET_ADMIN	Enable HTTP wallet create/import administration	false
N3INDEX_API_BASE_URL	Remote contract name lookup base URL	https://api.n3index.dev
N3INDEX_ENABLED	Enable N3Index-backed name resolution	true
HTTP_HOST	REST API listen address	127.0.0.1
HTTP_API_KEY	Bearer token for REST API routes	unset
HTTP_CORS_ORIGINS	Comma-separated exact HTTP/HTTPS origins	empty
HTTP_MAX_BODY_BYTES	Maximum HTTP request body size	1048576 (1 MiB)
MCP_HTTP_PORT	Remote MCP transport listen port	3001
MCP_HTTP_HOST	Remote MCP transport listen address	127.0.0.1
MCP_HTTP_PATH	Remote MCP endpoint path	/mcp
MCP_HTTP_BEARER	Bearer token for the remote MCP endpoint; required unless MCP_HTTP_HOST is loopback	unset
MCP_HTTP_ALLOWED_ORIGINS	Comma-separated exact origins allowed to connect from a browser	empty
MCP_HTTP_MAX_SESSIONS	Concurrent remote MCP session cap	128
MCP_HTTP_SESSION_TTL_MS	Idle remote MCP session expiry	1800000 (30 minutes)
WALLETS_DIR	Directory for persisted encrypted wallet records	./wallets
RATE_LIMITING_ENABLED	Enable request rate limiting	enabled outside test environments
MAX_REQUESTS_PER_MINUTE	Per-client minute limit	60
MAX_REQUESTS_PER_HOUR	Per-client hour limit	1000
LOG_LEVEL	debug, info, warn, or error	info
LOG_CONSOLE	Enable console logging	enabled outside test environments
LOG_FILE	Log file path; setting it enables file logging	./logs/neo-n3-mcp.log
LOG_FILE_ENABLED	Enable file logging without setting LOG_FILE	false
PORT	HTTP listen port	3000

The aliases NEO_MAINNET_RPC_URL, NEO_TESTNET_RPC_URL, and NEO_NETWORK_MODE remain supported.

Remote RPC endpoints must use HTTPS. Plain HTTP is accepted for loopback RPC endpoints; setting NEO_ALLOW_INSECURE_RPC=true explicitly permits remote plaintext HTTP and should be limited to controlled development environments.

When NEO_NETWORK=both, read-only MCP calls without an explicit network use mainnet. Every state-changing call requires an explicit network and an idempotency key. The HTTP entrypoint rejects both; set NEO_NETWORK=mainnet or NEO_NETWORK=testnet.

Writes are disabled by default. To enable them, create an owner-only signer file outside the repository and configure durable state:

install -m 0600 /dev/stdin /run/secrets/neo-signer-wif
export NEO_ENABLE_WRITES=true
export NEO_SIGNER_WIF_FILE=/run/secrets/neo-signer-wif
export NEO_WRITE_STATE_DIR=/var/lib/neo-n3-mcp/write-operations
export HTTP_WRITE_APPROVAL_API_KEY="$(openssl rand -hex 32)"

The MCP and HTTP request schemas never accept WIFs, private keys, or passwords. MCP writes require form elicitation and exact fingerprint approval. HTTP writes return a pending intent and require a separate approval request authenticated by HTTP_WRITE_APPROVAL_API_KEY.

HTTP API

This is a bespoke REST/JSON API, not an MCP transport. MCP clients cannot connect to it; they use the stdio entrypoint or the remote MCP transport.

Build and start the HTTP entrypoint:

npm ci
npm run build
export HTTP_API_KEY="$(openssl rand -hex 32)"
NEO_NETWORK=mainnet npm run start:http

The server listens on 127.0.0.1:3000 by default. A non-loopback HTTP_HOST requires HTTP_API_KEY, and every configured API key must contain at least 32 bytes. When a key is configured, send it as a bearer token on every route except GET /live and GET /health:

curl http://127.0.0.1:3000/live
curl http://127.0.0.1:3000/health
curl -H "Authorization: Bearer $HTTP_API_KEY" \
  http://127.0.0.1:3000/api/blockchain/height

The HTTP listener does not terminate TLS. Plaintext HTTP is supported only on loopback or a trusted host-local proxy network. Remote clients must use HTTPS through a TLS-terminating reverse proxy or load balancer; direct remote plaintext HTTP is unsupported because bearer tokens traverse requests.

The height endpoint distinguishes the node's block count from the latest block index:

{
  "blockCount": 12346,
  "height": 12345
}

HTTP_CORS_ORIGINS is an optional exact-origin allowlist. For example:

HTTP_CORS_ORIGINS=https://console.example.com,https://admin.example.com

Origins must use HTTP or HTTPS and cannot contain paths, credentials, query strings, or fragments. Wildcard CORS is not supported.

POST and PUT bodies must be JSON objects. The default body limit is 1 MiB and can be changed with HTTP_MAX_BODY_BYTES. A write request creates an immutable pending intent:

curl -X POST http://127.0.0.1:3000/api/transfers \
  -H "Authorization: Bearer $HTTP_API_KEY" \
  -H "Idempotency-Key: transfer-2026-07-11-001" \
  -H 'Content-Type: application/json' \
  -d '{"network":"mainnet","toAddress":"Nb...","asset":"NEO","amount":"1"}'

Approve only after comparing the returned fingerprint with the intended request:

curl -X POST http://127.0.0.1:3000/api/write-intents/INTENT_ID/approve \
  -H "Authorization: Bearer $HTTP_WRITE_APPROVAL_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{"fingerprint":"RETURNED_64_HEX_FINGERPRINT"}'

See API.md for the tool and route reference.

Remote MCP over Streamable HTTP

The Streamable HTTP transport serves the same MCP tools as the stdio entrypoint to remote MCP clients. It is a separate process from the REST API above, listens on its own port, and has its own configuration and bearer token.

npm ci
npm run build
export MCP_HTTP_BEARER="$(openssl rand -hex 32)"
NEO_NETWORK=mainnet npm run start:mcp-http

The server listens on 127.0.0.1:3001 by default and exposes:

Method	Path	Purpose
POST	MCP_HTTP_PATH (default /mcp)	JSON-RPC messages: initialize, tools/list, tools/call
GET	MCP_HTTP_PATH	Server-Sent Events stream for server-initiated messages
DELETE	MCP_HTTP_PATH	Terminates the session named by Mcp-Session-Id
GET	/healthz	Unauthenticated liveness probe

A non-loopback MCP_HTTP_HOST requires MCP_HTTP_BEARER and rejects a token shorter than 32 bytes, mirroring the HTTP_API_KEY rule for the REST entrypoint. When a token is configured, clients send Authorization: Bearer <token> on every request to MCP_HTTP_PATH; /healthz stays unauthenticated so probes can reach it.

Connect with the MCP TypeScript SDK:

import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';

const transport = new StreamableHTTPClientTransport(new URL('http://127.0.0.1:3001/mcp'), {
  requestInit: { headers: { Authorization: `Bearer ${process.env.MCP_HTTP_BEARER}` } },
});
const client = new Client({ name: 'my-client', version: '1.0.0' }, { capabilities: {} });
await client.connect(transport);
const { tools } = await client.listTools();

Like the REST listener, this listener serves plaintext HTTP and does not terminate TLS. Remote clients must reach it through a TLS-terminating reverse proxy. Sessions are held in memory, so a multi-replica deployment needs sticky routing on the Mcp-Session-Id header.

See remote-mcp-transport.md for the full configuration reference, an end-to-end local run against the Neo Explorer agent, production deployment guidance, and troubleshooting.

Docker

The production Compose file is docker/docker-compose.yml. It defines two services from the same image: neo-mcp runs the REST API on port 3000, and neo-mcp-http runs the remote MCP transport on port 3001. Each requires its own token, binds the host port to 127.0.0.1 by default, and persists wallet records in its own volume:

export HTTP_API_KEY="$(openssl rand -hex 32)"
export MCP_HTTP_BEARER="$(openssl rand -hex 32)"
docker compose -f docker/docker-compose.yml up -d

Start only the remote MCP service. Compose interpolates the whole file before selecting a service, so the REST service's mandatory HTTP_API_KEY must be set to any non-empty placeholder even though its container is never started here (the ">= 32 bytes" check only runs when that container actually starts):

HTTP_API_KEY=unused-when-starting-only-the-mcp-service \
MCP_HTTP_BEARER="$(openssl rand -hex 32)" \
  docker compose -f docker/docker-compose.yml up -d neo-mcp-http

To run a published image instead of building the checkout, use the digest-only registry overlay with the image repository and the release artifact's 64-character lowercase hexadecimal digest:

NEO_MCP_IMAGE_REPOSITORY=r3enetwork/neo-n3-mcp \
NEO_MCP_IMAGE_DIGEST=0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef \
HTTP_API_KEY="$HTTP_API_KEY" \
MCP_HTTP_BEARER="$MCP_HTTP_BEARER" \
  docker compose -f docker/docker-compose.yml \
    -f docker/docker-compose.registry.yml up -d

Set HTTP_BIND_ADDRESS=0.0.0.0 (REST) or MCP_HTTP_BIND_ADDRESS=0.0.0.0 (remote MCP) only when the service must be reachable by a TLS-terminating reverse proxy or load balancer. Do not expose either plaintext listener directly to remote clients.

The development Compose file binds locally and supplies local-development tokens by default. It defines neo-mcp-dev for the REST API and neo-mcp-http-dev for the remote MCP transport:

docker compose -f docker/docker-compose.dev.yml up -d

Those default tokens are for local development only. Override HTTP_API_KEY and MCP_HTTP_BEARER for any shared environment.

Build and run without Compose:

npm run docker:build
export HTTP_API_KEY="$(openssl rand -hex 32)"
npm run docker:run -- --detach

See DOCKER.md for image, volume, and helper-script details.

MCP Tools and Resources

The default MCP surface exposes 19 read-only tools. Enabling writes adds four tools, for 23 total:

• Network: get_network_mode
• Blockchain: get_blockchain_info, get_block_count, get_block, get_transaction, get_application_log, wait_for_transaction
• Wallet metadata: get_wallet
• Assets: get_balance, get_unclaimed_gas, get_nep17_transfers, get_nep11_balances, get_nep11_transfers, estimate_transfer_fees
• Contracts: invoke_contract, list_famous_contracts, get_contract_info, get_contract_status, estimate_invoke_fees
• Enabled writes: transfer_assets, invoke_contract_write, claim_gas, deploy_contract

The curated contract list is intentionally empty until each entry has a current network hash and a verified on-chain manifest. Generic contract tools accept a script hash, Neo address, exact N3Index name, or a name learned from a live manifest.

estimate_transfer_fees and estimate_invoke_fees return exact integer decimal strings in networkFeeDatos and systemFeeDatos, plus formatted GAS strings in networkFeeGas and systemFeeGas. Before any transaction is signed or broadcast, the combined system and network fee must not exceed NEO_MAX_TRANSACTION_FEE_GAS.

deploy_contract accepts compiler output as a complete serialized NEF object, nef: { encoding: "hex" | "base64", data: string }, together with its manifest. Raw VM bytecode is not a deployable NEF artifact.

get_block_count returns both blockCount and height, where height is max(0, blockCount - 1).

Resources:

• neo://network/status
• neo://mainnet/status
• neo://testnet/status
• neo://block/{height}

Security Notes

• Keep both HTTP listeners bound to loopback unless remote access is required.
• Terminate TLS before every remote HTTP connection; a bearer token authenticates requests but does not encrypt itself in transit.
• Use a randomly generated token of at least 32 bytes for HTTP_API_KEY and MCP_HTTP_BEARER.
• Keep NEO_ENABLE_WRITES=false on any remotely reachable MCP listener; the remote transport exists to serve read-only queries.
• Keep the signer WIF only in the owner-only NEO_SIGNER_WIF_FILE; never send it through MCP or HTTP.
• Persist WALLETS_DIR on controlled storage with restrictive permissions.
• State-changing MCP tools require an explicit network, a stable idempotency key, and exact form-elicited approval.
• Remote plaintext HTTP RPC endpoints are rejected unless NEO_ALLOW_INSECURE_RPC=true; prefer HTTPS.
• Signed transactions are rejected when their combined system and network fees exceed NEO_MAX_TRANSACTION_FEE_GAS.
• Rate limiting is enabled by default outside test-like environments.

Testing

# Deterministic unit tests; excludes tests/mcp-*.test.ts
npm run test:unit

# Compile, then run deterministic built-server smoke and lifecycle checks
npm run build
npm run test:mcp

# Unit tests + build + deterministic MCP checks
npm run test:all

# Opt-in public RPC checks; requires a build and network access
npm run build
npm run test:mcp:live

# Explicit stress suite; requires a build
npm run test:mcp:stress

npm run test:integration is an additional built-server integration script that calls public RPC endpoints; it is not part of test:all.

Release and Dependency Checks

npm audit and npm audit --omit=dev are expected to pass. The package uses a scoped lodash@4.18.1 override for the transitive @cityofzion/neon-core dependency.

./scripts/prepare-release.sh installs the lockfile, runs type checking, deterministic tests, the build, both audits, package validation, Compose validation, and container builds. It updates the version only after verification and does not create a commit or tag.

GitHub Actions tests Node.js 22 and 24. Published GitHub releases can publish the npm package and Docker image when the required repository secrets are configured; no production deployment target is defined in this repository.

Documentation

• API reference
• Remote MCP transport
• Deployment guide
• Docker guide
• Testing guide
• Production checklist
• Version management
• Architecture
• Networks
• Changelog

Troubleshooting

• Installation failures: verify node --version reports Node.js 22 or newer, then retry npm ci or the package install.
• HTTP_API_KEY is required: the HTTP process is listening on a non-loopback host. Set a key containing at least 32 bytes or bind HTTP_HOST to a loopback address.
• HTTP 401: send Authorization: Bearer <HTTP_API_KEY> on all routes except /live and /health.
• HTTP 413: reduce the request size or increase HTTP_MAX_BODY_BYTES to a positive integer.
• Remote MCP 401: send Authorization: Bearer <MCP_HTTP_BEARER>; /healthz is the only unauthenticated route.
• Remote MCP 404 after a successful initialize: the session expired, was evicted, or a proxy stripped the Mcp-Session-Id header. See remote-mcp-transport.md.
• RPC errors: verify the selected RPC URL is reachable and supports the requested Neo RPC method.

License

MIT. See LICENSE.