OPC UA Read Skill

When to Use This Skill

Load this skill when you need to:

•Read current sensor values from industrial equipment
•Monitor real-time process status
•Check equipment state and operational parameters
•Gather multiple data points for analysis or reporting
•Discover available sensors and variables in the OPC UA server

Quick Start

•Single Read: Use when you know the exact node ID
•Multiple Read: Use for batch reading multiple sensors (faster)
•Discovery: Use when you don't know the node IDs

Operations

1. Read a Single Node

When to use: You know the exact node ID and need one value.

How to do it:

json

{
  "action": "remote_tool_call",
  "target": "opcua",
  "params": {
    "agent_id": "local-dev",
    "connector_id": "opcua",
    "command": "read",
    "nodeId": "<node-id>"
  }
}

Default Connector ID: Use "opcua" as the standard connector ID.

Multiple OPC UA Servers: If the edge device has multiple OPC UA connectors, they should be named with suffixes: "opcua-line1", "opcua-line2", "opcua-lab", etc.

Node ID Format:

•
Numeric: ns=<namespace>;i=<number>
- •Example: ns=2;i=101 (namespace 2, identifier 101)
•
String: ns=<namespace>;s=<identifier>
- •Example: ns=3;s=Temperature_Sensor_1
•Server Status: ns=0;i=2259 (Server_ServerStatus_CurrentTime)

Returns:

json

{
  "value": 87.3,
  "dataType": "Double",
  "statusCode": "Good",
  "timestamp": "2026-01-14T10:30:00Z"
}

2. Read Multiple Nodes (Batch Read)

When to use: You need several values at once (more efficient than individual reads).

How to do it:

json

{
  "action": "remote_tool_call",
  "target": "opcua",
  "params": {
    "agent_id": "local-dev",
    "connector_id": "opcua",
    "command": "read_multiple",
    "nodeIds": [
      "ns=2;i=101",
      "ns=2;i=102",
      "ns=2;i=103"
    ]
  }
}

Returns:

json

{
  "ns=2;i=101": {
    "value": 87.3,
    "timestamp": "2026-01-14T10:30:00Z",
    "statusCode": "Good"
  },
  "ns=2;i=102": {
    "value": 2.5,
    "timestamp": "2026-01-14T10:30:00Z",
    "statusCode": "Good"
  },
  "ns=2;i=103": {
    "value": 125.8,
    "timestamp": "2026-01-14T10:30:00Z",
    "statusCode": "Good"
  }
}

3. Discover All Variables

When to use: You don't know what sensors are available.

How to do it:

json

{
  "action": "remote_tool_call",
  "target": "opcua",
  "params": {
    "agent_id": "local-dev",
    "connector_id": "opcua",
    "command": "get_all_variables"
  }
}

Returns:

json

[
  {
    "name": "Temperature",
    "nodeId": "ns=2;i=101",
    "value": 87.3,
    "dataType": "Double"
  },
  {
    "name": "Pressure",
    "nodeId": "ns=2;i=102",
    "value": 2.5,
    "dataType": "Double"
  }
]

4. Browse Node Hierarchy

When to use: You want to explore the node tree structure.

How to do it:

json

{
  "action": "remote_tool_call",
  "target": "opcua",
  "params": {
    "agent_id": "local-dev",
    "connector_id": "<opcua-connector-id>",
    "command": "browse",
    "nodeId": "i=85"
  }
}

Note: Leave nodeId empty or use "i=85" for ObjectsFolder (root).

Returns:

json

[
  {
    "nodeId": "ns=2;i=100",
    "browseName": "Sensors",
    "nodeClass": "Object",
    "displayName": "Sensor Group"
  },
  {
    "nodeId": "ns=2;i=101",
    "browseName": "Temperature",
    "nodeClass": "Variable",
    "displayName": "Reactor Temperature"
  }
]

Example Workflows

Workflow 1: Read Single Sensor

User Request: "What's the reactor temperature?"

Steps:

•Load this skill (opcua-read)
•Check references/common_nodes.md for reactor temperature node ID
•Use read command with nodeId: "ns=2;i=101"
•Format response: "The reactor temperature is 87.3°C"

Example Response:

code

The reactor temperature is 87.3°C (as of 10:30:00 AM)

Workflow 2: Monitor Multiple Motors

User Request: "Check all motor speeds on Production Line 1"

Steps:

•Load this skill (opcua-read)
•Use read_multiple with motor node IDs: ["ns=2;i=301", "ns=2;i=302", "ns=2;i=303", "ns=2;i=304", "ns=2;i=305"]
•Present results in table format

Example Response:

code

Production Line 1 - Motor Speeds:
┌─────────┬───────────┬────────┐
│ Motor   │ Speed     │ Status │
├─────────┼───────────┼────────┤
│ Motor 1 │ 1450 RPM  │ Good   │
│ Motor 2 │ 1445 RPM  │ Good   │
│ Motor 3 │ 1460 RPM  │ Good   │
│ Motor 4 │ 1455 RPM  │ Good   │
│ Motor 5 │ 1440 RPM  │ Good   │
└─────────┴───────────┴────────┘

Workflow 3: Discover and Filter

User Request: "Show me all temperature sensors in the system"

Steps:

•Load this skill (opcua-read)
•Use get_all_variables to get all variables
•Filter results where name contains "Temperature" or "Temp"
•Present filtered list with node IDs

Example Response:

code

Temperature Sensors Found:
1. Reactor Temperature (ns=2;i=101) - Current: 87.3°C
2. Cooling Water Temp (ns=2;i=201) - Current: 22.5°C
3. Outlet Temperature (ns=2;i=301) - Current: 45.2°C

Workflow 4: Read and Save Report

User Request: "Check all critical sensors and save a status report"

Steps:

•Load this skill (opcua-read)
•Use read_multiple for critical sensors
•Format data as markdown
•Use filesystem skill to write report

Example:

json

// Step 1: Read sensors
{
  "action": "remote_tool_call",
  "target": "opcua",
  "params": {
    "connector_id": "factory-opcua",
    "command": "read_multiple",
    "nodeIds": ["ns=2;i=101", "ns=2;i=102", "ns=2;i=201"]
  }
}

// Step 2: Write report
{
  "action": "remote_tool_call",
  "target": "filesystem",
  "params": {
    "command": "write",
    "path": "reports/sensor-status-2026-01-14.md",
    "content": "# Sensor Status Report\n\n..."
  }
}

Common Node IDs

See references/common_nodes.md for factory-specific node ID mappings.

Standard OPC UA Nodes:

•ns=0;i=2259 - Server_ServerStatus_CurrentTime
•ns=0;i=2256 - Server_ServerStatus_State
•i=85 - ObjectsFolder (root for browsing)

Data Types

Common OPC UA data types you'll encounter:

Data Type	Description	Example Value
`Double`	Floating point number	87.3
`Float`	Single-precision float	12.5
`Int32`	32-bit integer	1450
`Int16`	16-bit integer	255
`Boolean`	True/False	true
`String`	Text	"Running"
`DateTime`	Timestamp	"2026-01-14T10:30:00Z"

Status Codes

Good (0x00000000): Value is valid and reliable Uncertain: Value may not be accurate Bad: Value is invalid or unavailable

Always check the statusCode field in results.

Tips & Best Practices

1. Use Batch Reads

Instead of:

code

read(ns=2;i=101)
read(ns=2;i=102)
read(ns=2;i=103)

Do this:

code

read_multiple(["ns=2;i=101", "ns=2;i=102", "ns=2;i=103"])

2. Discovery First

If you don't know node IDs:

•Use get_all_variables to see what's available
•Or use browse to explore the hierarchy
•Then use specific node IDs for targeted reads

3. Check Status Codes

Always verify statusCode: "Good" before trusting the value.

4. Cache Node IDs

Once you discover a node ID, save it in your response for future reference.

5. Format Numbers Appropriately

•Temperature: 1 decimal place (87.3°C)
•Pressure: 2 decimal places (2.45 bar)
•RPM: Whole numbers (1450 RPM)
•Percentages: Whole numbers (75%)

Error Handling

Common Errors

Error: "Connector not found"

•Cause: Invalid connector_id
•Fix: Check available OPC UA connectors

Error: "Node not found"

•Cause: Invalid nodeId or node doesn't exist
•Fix: Use browse or get_all_variables to find correct node

Error: "Bad status code"

•Cause: Node exists but value is unavailable
•Fix: Check if sensor is connected and functioning

Error: "Connection timeout"

•Cause: OPC UA server unreachable
•Fix: Verify server is running and network is accessible

Scripts

read_node.py (Optional)

Helper script for formatted output:

bash

python scripts/read_node.py <connector_id> <nodeId>

Returns human-readable formatted output based on data type.

References

•common_nodes.md: Factory-specific node ID reference
•node_id_format.md: Complete guide to OPC UA node ID syntax

Related Skills

•opcua-write: For control operations (writing setpoints)
•opcua-discovery: For advanced node exploration
•opcua-historian: For historical trend analysis
•opcua-diagnostics: For health monitoring

Version History

1.0.0 (2026-01-14)

•Initial release
•Basic read operations
•Discovery capabilities