bridge-mcp-server

trace_tag

Traces a single Ignition SCADA tag through OPC and Studio 5000 L5X mapping to every PLC logic rung. Returns the full signal chain from SCADA config to PLC logic.

Instructions

Trace a single tag end-to-end: Ignition config → OPC path → L5X tag → PLC logic.

Returns the complete signal chain showing where the tag is defined in Ignition, what PLC tag it maps to, and every rung/line of PLC logic that references it.

Args: ignition_path: Path to Ignition project directory or .zip export. l5x_path: Path to Studio 5000 .l5x file. tag_name: Ignition tag name to trace (e.g. "Running", "Conveyors/Line1/Speed"). mapping_file: Optional JSON file with explicit tag mappings.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "ignition_path": "<ignition_path>",
      "l5x_path": "<l5x_path>",
      "tag_name": "<tag_name>"
    },
    "name": "trace_tag"
  }
}

Input Schema

Name	Required	Description	Default
`l5x_path`	Yes
`tag_name`	Yes
`mapping_file`	No
`ignition_path`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.4.0Oct 20, 2026

TDQS

A3.7/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly states what the tool returns (the signal chain and referenced PLC logic) and 'Trace' suggests a read/analysis operation, but it never explicitly states that the tool is read-only or describes side effects, failure modes, or environment expectations. This is adequate but not fully transparent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with purpose and return behavior, followed by a clean, structured Args block. There is no filler or irrelevant detail; every sentence earns its place, and the parameter list makes the interface immediately scannable.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with four parameters and an output schema, the description covers the main operational needs: what the tool does, what it returns, and what each argument means. It omits some edge-case context such as expected file validity, behavior when the tag is not found, or the exact format of the mapping file, but the presence of an output schema reduces the burden for return-value details.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate, and it does: all four parameters are listed with meaningful explanations. It communicates path formats, the optionality of mapping_file, and gives a concrete example for tag_name, fully covering what the schema omits.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb and resource: 'Trace a single tag end-to-end' and lays out the exact chain (Ignition config → OPC path → L5X tag → PLC logic). It clearly distinguishes this as a single-tag tracing tool, though it does not explicitly name or contrast sibling tools like find_unmapped_tags.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies a use case—when you need to trace one tag's full signal chain—but provides no explicit guidance on when to choose this tool over alternatives. It gives no exclusions, prerequisites, or references to sibling tools, leaving the selection decision mostly to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server