kicad-mcp-layer

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sch_trace

Read-onlyIdempotent

Lists each pin's net and all other pins on that net for a given reference designator, using the cached netlist. Unconnected pins return null.

Instructions

For one component, list each pin's net and everything else on that net. Unconnected pins have net null. Uses the cached netlist.

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": {
      "schematic_path": "<schematic_path>",
      "ref": "<ref>"
    },
    "name": "sch_trace"
  }
}

Input Schema

Name	Required	Description
`pin`	No	Pin number to restrict to; all pins when omitted.
`ref`	Yes	Reference designator, e.g. U1 or R12.
`schematic_path`	Yes	A .kicad_sch file, absolute or relative to the workspace. Any sheet of the project works; the root sheet is used.

Output Schema

Name	Required	Description	Default
`ref`	Yes
`pins`	Yes
`value`	Yes
`footprint`	Yes
`sheet_path`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 12, 2026

TDQS

A3.8/5.0

Behavior4/5

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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds genuinely useful behavior beyond them: unconnected pins return net=null, and results come from the cached netlist (a staleness/precondition caveat). It does not state what the cache-read implies for freshness, but the added context is substantive.

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?

Three short sentences, front-loaded with the core action, then the null-pin edge case, then the caching note. No filler or redundancy.

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?

With an output schema present, annotations covering safety, and full schema descriptions, the description's job is mostly to add edge-case and precondition context, which it does (null nets, cached netlist). Only the freshness/lifecycle of the cache is unaddressed, keeping it just short of 5.

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

Parameters3/5

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

Schema coverage is 100%, so the schema already documents ref, pin, and schematic_path. The description only reinforces the single-component scope and the 'all pins when omitted' behavior, adding little beyond the schema. Baseline 3 applies.

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 gives a specific verb and resource: list each pin's net and all other members of that net, scoped to one component. That is clearly distinct from sch_netlist (whole-project netlist) even though the sibling is not named. It stops short of explicit sibling routing, so 4 rather than 5.

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

Usage Guidelines3/5

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

Usage is implied by 'for one component' versus a whole-netlist tool, and 'Uses the cached netlist' hints at a prerequisite (a netlist must already be built). However, no explicit when-to-use/when-not or named alternative (e.g., sch_netlist) is given, so this is minimum-viable guidance.

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