OPC UA MCP Server

io.github.midhunxavier/opcua · v0.6.0

Connect AI assistants to industrial OPC UA: browse, read, history, subscriptions, events and alarms.

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Connect Runs on your machine

Terminal

claude mcp add opcua -e OPCUA_SERVER_URL=<OPCUA_SERVER_URL> -e OPCUA_PYTHON_BACKEND=<OPCUA_PYTHON_BACKEND> -e OPCUA_SECURITY_POLICY=<OPCUA_SECURITY_POLICY> -e OPCUA_SECURITY_MODE=<OPCUA_SECURITY_MODE> -e OPCUA_CLIENT_CERT=<OPCUA_CLIENT_CERT> -e OPCUA_CLIENT_KEY=<OPCUA_CLIENT_KEY> -e OPCUA_APPLICATION_URI=<OPCUA_APPLICATION_URI> -e OPCUA_SERVER_CERT=<OPCUA_SERVER_CERT> -e OPCUA_SERVER_TRUST_STORE=<OPCUA_SERVER_TRUST_STORE> -e OPCUA_SERVER_APPLICATION_URI=<OPCUA_SERVER_APPLICATION_URI> -e OPCUA_USERNAME=<OPCUA_USERNAME> -e OPCUA_PASSWORD=<OPCUA_PASSWORD> -e OPCUA_USER_CERT=<OPCUA_USER_CERT> -e OPCUA_USER_KEY=<OPCUA_USER_KEY> -e OPCUA_PROFILE=<OPCUA_PROFILE> -e OPCUA_POLICY_FILE=<OPCUA_POLICY_FILE> -e OPCUA_ALLOWED_TOOLS=<OPCUA_ALLOWED_TOOLS> -e OPCUA_ALLOWED_WRITE_NODES=<OPCUA_ALLOWED_WRITE_NODES> -e OPCUA_ALLOWED_METHODS=<OPCUA_ALLOWED_METHODS> -e OPCUA_ALLOW_ACKNOWLEDGE_ALARMS=<OPCUA_ALLOW_ACKNOWLEDGE_ALARMS> -e OPCUA_ALLOW_INSECURE_CONTROL=<OPCUA_ALLOW_INSECURE_CONTROL> -e OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL=<OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL> -e OPCUA_ALLOW_OUT_OF_RANGE_WRITES=<OPCUA_ALLOW_OUT_OF_RANGE_WRITES> -e OPCUA_AUDIT_FILE=<OPCUA_AUDIT_FILE> -e OPCUA_AUDIT_FSYNC=<OPCUA_AUDIT_FSYNC> -e OPCUA_AUDIT_CHAIN=<OPCUA_AUDIT_CHAIN> -e OPCUA_AUDIT_CHAIN_KEY_FILE=<OPCUA_AUDIT_CHAIN_KEY_FILE> -e OPCUA_OPERATOR_ID=<OPCUA_OPERATOR_ID> -e OPCUA_RECONNECT_INITIAL_DELAY_MS=<OPCUA_RECONNECT_INITIAL_DELAY_MS> -e OPCUA_RECONNECT_MAX_DELAY_MS=<OPCUA_RECONNECT_MAX_DELAY_MS> -e OPCUA_RECONNECT_MAX_RETRY=<OPCUA_RECONNECT_MAX_RETRY> -e OPCUA_SESSION_TIMEOUT_MS=<OPCUA_SESSION_TIMEOUT_MS> -- npx -y [email protected]

claude_desktop_config.json

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": [
        "-y",
        "[email protected]"
      ],
      "env": {
        "OPCUA_SERVER_URL": "<OPCUA_SERVER_URL>",
        "OPCUA_PYTHON_BACKEND": "<OPCUA_PYTHON_BACKEND>",
        "OPCUA_SECURITY_POLICY": "<OPCUA_SECURITY_POLICY>",
        "OPCUA_SECURITY_MODE": "<OPCUA_SECURITY_MODE>",
        "OPCUA_CLIENT_CERT": "<OPCUA_CLIENT_CERT>",
        "OPCUA_CLIENT_KEY": "<OPCUA_CLIENT_KEY>",
        "OPCUA_APPLICATION_URI": "<OPCUA_APPLICATION_URI>",
        "OPCUA_SERVER_CERT": "<OPCUA_SERVER_CERT>",
        "OPCUA_SERVER_TRUST_STORE": "<OPCUA_SERVER_TRUST_STORE>",
        "OPCUA_SERVER_APPLICATION_URI": "<OPCUA_SERVER_APPLICATION_URI>",
        "OPCUA_USERNAME": "<OPCUA_USERNAME>",
        "OPCUA_PASSWORD": "<OPCUA_PASSWORD>",
        "OPCUA_USER_CERT": "<OPCUA_USER_CERT>",
        "OPCUA_USER_KEY": "<OPCUA_USER_KEY>",
        "OPCUA_PROFILE": "<OPCUA_PROFILE>",
        "OPCUA_POLICY_FILE": "<OPCUA_POLICY_FILE>",
        "OPCUA_ALLOWED_TOOLS": "<OPCUA_ALLOWED_TOOLS>",
        "OPCUA_ALLOWED_WRITE_NODES": "<OPCUA_ALLOWED_WRITE_NODES>",
        "OPCUA_ALLOWED_METHODS": "<OPCUA_ALLOWED_METHODS>",
        "OPCUA_ALLOW_ACKNOWLEDGE_ALARMS": "<OPCUA_ALLOW_ACKNOWLEDGE_ALARMS>",
        "OPCUA_ALLOW_INSECURE_CONTROL": "<OPCUA_ALLOW_INSECURE_CONTROL>",
        "OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL": "<OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL>",
        "OPCUA_ALLOW_OUT_OF_RANGE_WRITES": "<OPCUA_ALLOW_OUT_OF_RANGE_WRITES>",
        "OPCUA_AUDIT_FILE": "<OPCUA_AUDIT_FILE>",
        "OPCUA_AUDIT_FSYNC": "<OPCUA_AUDIT_FSYNC>",
        "OPCUA_AUDIT_CHAIN": "<OPCUA_AUDIT_CHAIN>",
        "OPCUA_AUDIT_CHAIN_KEY_FILE": "<OPCUA_AUDIT_CHAIN_KEY_FILE>",
        "OPCUA_OPERATOR_ID": "<OPCUA_OPERATOR_ID>",
        "OPCUA_RECONNECT_INITIAL_DELAY_MS": "<OPCUA_RECONNECT_INITIAL_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_DELAY_MS": "<OPCUA_RECONNECT_MAX_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_RETRY": "<OPCUA_RECONNECT_MAX_RETRY>",
        "OPCUA_SESSION_TIMEOUT_MS": "<OPCUA_SESSION_TIMEOUT_MS>"
      }
    }
  }
}

~/.cursor/mcp.json

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": [
        "-y",
        "[email protected]"
      ],
      "env": {
        "OPCUA_SERVER_URL": "<OPCUA_SERVER_URL>",
        "OPCUA_PYTHON_BACKEND": "<OPCUA_PYTHON_BACKEND>",
        "OPCUA_SECURITY_POLICY": "<OPCUA_SECURITY_POLICY>",
        "OPCUA_SECURITY_MODE": "<OPCUA_SECURITY_MODE>",
        "OPCUA_CLIENT_CERT": "<OPCUA_CLIENT_CERT>",
        "OPCUA_CLIENT_KEY": "<OPCUA_CLIENT_KEY>",
        "OPCUA_APPLICATION_URI": "<OPCUA_APPLICATION_URI>",
        "OPCUA_SERVER_CERT": "<OPCUA_SERVER_CERT>",
        "OPCUA_SERVER_TRUST_STORE": "<OPCUA_SERVER_TRUST_STORE>",
        "OPCUA_SERVER_APPLICATION_URI": "<OPCUA_SERVER_APPLICATION_URI>",
        "OPCUA_USERNAME": "<OPCUA_USERNAME>",
        "OPCUA_PASSWORD": "<OPCUA_PASSWORD>",
        "OPCUA_USER_CERT": "<OPCUA_USER_CERT>",
        "OPCUA_USER_KEY": "<OPCUA_USER_KEY>",
        "OPCUA_PROFILE": "<OPCUA_PROFILE>",
        "OPCUA_POLICY_FILE": "<OPCUA_POLICY_FILE>",
        "OPCUA_ALLOWED_TOOLS": "<OPCUA_ALLOWED_TOOLS>",
        "OPCUA_ALLOWED_WRITE_NODES": "<OPCUA_ALLOWED_WRITE_NODES>",
        "OPCUA_ALLOWED_METHODS": "<OPCUA_ALLOWED_METHODS>",
        "OPCUA_ALLOW_ACKNOWLEDGE_ALARMS": "<OPCUA_ALLOW_ACKNOWLEDGE_ALARMS>",
        "OPCUA_ALLOW_INSECURE_CONTROL": "<OPCUA_ALLOW_INSECURE_CONTROL>",
        "OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL": "<OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL>",
        "OPCUA_ALLOW_OUT_OF_RANGE_WRITES": "<OPCUA_ALLOW_OUT_OF_RANGE_WRITES>",
        "OPCUA_AUDIT_FILE": "<OPCUA_AUDIT_FILE>",
        "OPCUA_AUDIT_FSYNC": "<OPCUA_AUDIT_FSYNC>",
        "OPCUA_AUDIT_CHAIN": "<OPCUA_AUDIT_CHAIN>",
        "OPCUA_AUDIT_CHAIN_KEY_FILE": "<OPCUA_AUDIT_CHAIN_KEY_FILE>",
        "OPCUA_OPERATOR_ID": "<OPCUA_OPERATOR_ID>",
        "OPCUA_RECONNECT_INITIAL_DELAY_MS": "<OPCUA_RECONNECT_INITIAL_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_DELAY_MS": "<OPCUA_RECONNECT_MAX_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_RETRY": "<OPCUA_RECONNECT_MAX_RETRY>",
        "OPCUA_SESSION_TIMEOUT_MS": "<OPCUA_SESSION_TIMEOUT_MS>"
      }
    }
  }
}

.vscode/mcp.json

{
  "servers": {
    "opcua": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "[email protected]"
      ],
      "env": {
        "OPCUA_SERVER_URL": "<OPCUA_SERVER_URL>",
        "OPCUA_PYTHON_BACKEND": "<OPCUA_PYTHON_BACKEND>",
        "OPCUA_SECURITY_POLICY": "<OPCUA_SECURITY_POLICY>",
        "OPCUA_SECURITY_MODE": "<OPCUA_SECURITY_MODE>",
        "OPCUA_CLIENT_CERT": "<OPCUA_CLIENT_CERT>",
        "OPCUA_CLIENT_KEY": "<OPCUA_CLIENT_KEY>",
        "OPCUA_APPLICATION_URI": "<OPCUA_APPLICATION_URI>",
        "OPCUA_SERVER_CERT": "<OPCUA_SERVER_CERT>",
        "OPCUA_SERVER_TRUST_STORE": "<OPCUA_SERVER_TRUST_STORE>",
        "OPCUA_SERVER_APPLICATION_URI": "<OPCUA_SERVER_APPLICATION_URI>",
        "OPCUA_USERNAME": "<OPCUA_USERNAME>",
        "OPCUA_PASSWORD": "<OPCUA_PASSWORD>",
        "OPCUA_USER_CERT": "<OPCUA_USER_CERT>",
        "OPCUA_USER_KEY": "<OPCUA_USER_KEY>",
        "OPCUA_PROFILE": "<OPCUA_PROFILE>",
        "OPCUA_POLICY_FILE": "<OPCUA_POLICY_FILE>",
        "OPCUA_ALLOWED_TOOLS": "<OPCUA_ALLOWED_TOOLS>",
        "OPCUA_ALLOWED_WRITE_NODES": "<OPCUA_ALLOWED_WRITE_NODES>",
        "OPCUA_ALLOWED_METHODS": "<OPCUA_ALLOWED_METHODS>",
        "OPCUA_ALLOW_ACKNOWLEDGE_ALARMS": "<OPCUA_ALLOW_ACKNOWLEDGE_ALARMS>",
        "OPCUA_ALLOW_INSECURE_CONTROL": "<OPCUA_ALLOW_INSECURE_CONTROL>",
        "OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL": "<OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL>",
        "OPCUA_ALLOW_OUT_OF_RANGE_WRITES": "<OPCUA_ALLOW_OUT_OF_RANGE_WRITES>",
        "OPCUA_AUDIT_FILE": "<OPCUA_AUDIT_FILE>",
        "OPCUA_AUDIT_FSYNC": "<OPCUA_AUDIT_FSYNC>",
        "OPCUA_AUDIT_CHAIN": "<OPCUA_AUDIT_CHAIN>",
        "OPCUA_AUDIT_CHAIN_KEY_FILE": "<OPCUA_AUDIT_CHAIN_KEY_FILE>",
        "OPCUA_OPERATOR_ID": "<OPCUA_OPERATOR_ID>",
        "OPCUA_RECONNECT_INITIAL_DELAY_MS": "<OPCUA_RECONNECT_INITIAL_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_DELAY_MS": "<OPCUA_RECONNECT_MAX_DELAY_MS>",
        "OPCUA_RECONNECT_MAX_RETRY": "<OPCUA_RECONNECT_MAX_RETRY>",
        "OPCUA_SESSION_TIMEOUT_MS": "<OPCUA_SESSION_TIMEOUT_MS>"
      }
    }
  }
}

Replace the values in angle brackets with your own. Keys stay on your machine; we never see them.

Tools

This server runs locally, so its tools are listed by your MCP client once it starts.

Environment variables

Name	Description
`OPCUA_SERVER_URL` Required	URL of the OPC UA server to connect to, including any path the server expects. Read once at startup: one process serves one endpoint. Verify who answers with an exact server certificate pin or a configured CA trust store.
`OPCUA_PYTHON_BACKEND` Optional	Select the Python client implementation. The maintained asyncua client is the default; legacy provides the one-release rollback path for uncovered vendor incompatibilities. This setting affects the Python server only.
`OPCUA_SECURITY_POLICY` Optional	Encryption suite to negotiate for the secure channel. Anything other than None needs a client certificate and key. The two AES suites are Node-only: the Python runtime refuses them at startup rather than downgrading. None is unencrypted and unauthenticated, and keeps control tools blocked unless in…
`OPCUA_SECURITY_MODE` Optional	Message security mode for the secure channel. Sign authenticates messages without encrypting them. A policy with mode None, or a mode without a policy, stops the server at startup; leaving it blank never downgrades a policy to signing only. Leave blank for SignAndEncrypt once a security policy is s…
`OPCUA_CLIENT_CERT` Optional	Path to the certificate (PEM or DER) this client presents as its application identity. Required by any security policy other than None. A path that does not exist stops the server at startup.
`OPCUA_CLIENT_KEY` Optional, secret	Path to the private key matching the client certificate. A path, never key material. Whoever can read the file can impersonate this client: keep it readable only by the account running the server. A path that does not exist stops the server at startup.
`OPCUA_APPLICATION_URI` Optional	Application URI announced to the server. Set it only for a certificate that carries no URI of its own. A configured URI that conflicts with the certificate is refused before connecting. Leave blank for the subjectAltName URI of the client certificate.
`OPCUA_SERVER_CERT` Optional	Path to the OPC UA server's own certificate (PEM or DER), pinned: a server presenting any other certificate cannot complete the handshake. Control tools (writes, method calls, alarm actions) require it, or OPCUA_SERVER_TRUST_STORE instead. Requires a security policy other than None. Unset, encrypti…
`OPCUA_SERVER_TRUST_STORE` Optional	Directory with trusted/certs root CAs, issuers/certs intermediate CAs, and trusted/crl plus issuers/crl signed current revocation lists. Authenticate the OPC UA peer by its validated chain and expected server URI. Requires secured channel and OPCUA_SERVER_APPLICATION_URI; Python requires the mainta…
`OPCUA_SERVER_APPLICATION_URI` Optional	ApplicationUri of the intended OPC UA server. Must match the peer certificate URI SAN and advertised application identity. Required with OPCUA_SERVER_TRUST_STORE.
`OPCUA_USERNAME` Optional	OPC UA username. The session is anonymous when unset. Cannot be combined with a user certificate. Requires a password; either one alone stops the server at startup.
`OPCUA_PASSWORD` Optional, secret	Password for the username. Without a security policy it crosses the network in clear text. Supply it through the client's secret storage, never on a command line.
`OPCUA_USER_CERT` Optional	Path to the certificate identifying the user, for X.509 user authentication: a different key pair from the client certificate, which secures the channel. Requires the user key and a security policy other than None; cannot be combined with a username. Any of those combinations broken stops the serve…
`OPCUA_USER_KEY` Optional, secret	Path to the private key for the user certificate. It signs the server's challenge and is never sent. Whoever can read the file can log in as this user: keep it readable only by the account running the server.
`OPCUA_PROFILE` Required	Which tools are offered. observe reads, browses, reads history and monitors; operator adds explicitly allowlisted writes, method calls and alarm actions; full exposes every tool and is meant only for a tightly scoped OPC UA account. Unset fails closed to observe; an unknown profile stops the server…
`OPCUA_POLICY_FILE` Optional	Path to a version-1 JSON policy file, the only place per-node value bounds, writable_subtrees, preconditions, the alarm scope and deny_read can be set. Every policy variable that is set overrides what the file says. An unreadable or invalid file stops the server at startup.
`OPCUA_ALLOWED_TOOLS` Optional	Comma-separated tool allowlist. It can only narrow the selected profile, never widen it. An unknown tool name stops the server at startup.
`OPCUA_ALLOWED_WRITE_NODES` Optional	Comma-separated exact node IDs the operator profile may write, as ns=2;i=5 or, stable across a server restart, nsu=<namespace-uri>;i=5 or a browse path from the Root folder such as /Objects/Line1/Setpoint. Setting it replaces the policy file's list, bounds included. Empty fails closed: operator can…
`OPCUA_ALLOWED_METHODS` Optional	Comma-separated object_node_id\|method_node_id pairs the operator profile may call. Either half may be a browse path from the Root folder. Empty fails closed: operator can call nothing. An entry without \| stops the server at startup.
`OPCUA_ALLOW_ACKNOWLEDGE_ALARMS` Optional	Let the operator profile act on alarms: acknowledge_alarm and every act_on_alarm action.
`OPCUA_ALLOW_INSECURE_CONTROL` Optional	Permit control tools on an OPC UA channel with no security policy (None). Does not cover a secured channel to an unverified server; that is OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL. Fail-open override: writes, method calls and alarm actions then travel unauthenticated and unencrypted. Reported as cont…
`OPCUA_ALLOW_UNVERIFIED_SERVER_CONTROL` Optional	Permit control tools on a secured OPC UA channel whose server is not authenticated: neither pinned with OPCUA_SERVER_CERT nor validated by OPCUA_SERVER_TRUST_STORE. Does not cover a channel with no security policy; that is OPCUA_ALLOW_INSECURE_CONTROL. Fail-open override: writes, method calls and a…
`OPCUA_ALLOW_OUT_OF_RANGE_WRITES` Optional	Allow a write outside the EURange the OPC UA server itself published for the node. A published InstrumentRange still applies. Fail-open override: it discards the only value bound a deployment with no policy file has.
`OPCUA_AUDIT_FILE` Optional	Path to an append-only file for the control audit trail, one JSON object per line, written beside stderr. Created owner-only (0600) if it does not exist; reopened when rotated away. A file that cannot be opened, or that is a symlink, not a regular file, another account's, or group/world-writable, s…
`OPCUA_AUDIT_FSYNC` Optional	When an audit-file record counts as written. always fsyncs each record before the control call proceeds, so it survives a power loss; none leaves it to the operating system, so it survives only a crash of this process. none can lose the records of control calls that already reached the plant if the…
`OPCUA_AUDIT_CHAIN` Optional	Adds seq, prev_hash and hash to every audit record so edits, deletions and reordering can be detected with --verify-audit. sha256 catches accidental or naive edits; hmac-sha256 also resists anyone without the key. Requires the audit file. Set without an audit file, or hmac-sha256 without a key file…
`OPCUA_AUDIT_CHAIN_KEY_FILE` Optional, secret	Path to the HMAC key for the hmac-sha256 audit chain: at least 32 bytes, for example from openssl rand -hex 32. Surrounding whitespace is ignored. Whoever can read the key can forge the chain: a key readable or writable by group or others stops the server. Refused unless the chain is hmac-sha256.
`OPCUA_OPERATOR_ID` Optional	Label stamped on every audit record as operator_label, so a shipped log says which deployment a control call came from. Configured, never verified: it is not an identity, and mcp_principal stays null.
`OPCUA_RECONNECT_INITIAL_DELAY_MS` Optional	Wait before the first attempt to repair a dropped or refused connection, in milliseconds. It doubles with each further attempt.
`OPCUA_RECONNECT_MAX_DELAY_MS` Optional	Ceiling for the doubling retry delay, in milliseconds.
`OPCUA_RECONNECT_MAX_RETRY` Optional	Retries after the first attempt, per connection round, before a tool call gives up: a whole number from -1 to 1000. 0 never retries; -1 never stops trying, in bounded rounds of four retries so no single call waits forever.
`OPCUA_SESSION_TIMEOUT_MS` Optional	Session lifetime asked of the OPC UA server, in milliseconds. It also sets the keep-alive period, so it decides how quickly an idle connection notices the server has gone.

Details

Package	`[email protected]` (NPM, stdio)
First published	5 Nov 2026
Last updated	5 Nov 2026
Registry name	`io.github.midhunxavier/opcua`

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