calc.engineer

trace width

trace_width

Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula. The IPC-2221 empirical equation relates current capacity to cross-sectional area and temperature rise: I = k * dT^0.44 * A^0.725, where k=0.048 for external layers and k=0.024 for internal layers. Supports configurable copper weight (oz/ft^2) and temperature rise. Also computes approximate DC resistance per centimeter. Essential for power delivery, high-current motor drivers, and ensuring PCB reliability. Chain from voltage_divider or impedance_match to verify trace sizing for computed currents.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`layer`	No	PCB layer type. External layers dissipate heat better (k=0.048); internal layers use k=0.024.	external
`copper_oz`	No	Copper weight in ounces per square foot. 1 oz/ft^2 = 1.37 mil (34.8 um) thickness. Common values: 0.5, 1, 2.
`temp_rise_c`	No	Allowable temperature rise above ambient in degrees Celsius. IPC-2221 standard uses 10, 20, or 30 C.
`current_amps`	Yes	Required current capacity in amperes (A).

Output Schema

TableJSON Schema

Name	Required	Description
`width_mm`	Yes	Required trace width in millimeters.
`area_mil2`	Yes	Required cross-sectional area in square mils.
`width_mil`	Yes	Required trace width in mils (thousandths of an inch).
`resistance_per_cm_mohm`	Yes	Approximate DC resistance per centimeter of trace in milliohms, using copper resistivity.

TDQS

A4.5/5.0

Behavior4/5

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

With no annotations, the description bears full burden. It discloses the IPC-2221 formula, constants for internal/external layers, and mentions additional DC resistance output. It could be more explicit about input validation or limitations, but the level of detail is good for a calculation tool.

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 efficient: four sentences cover purpose, formula, parameters, output, use cases, and chaining. No unnecessary words; every sentence earns its place.

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

Completeness5/5

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

Given the output schema exists, the description need not explain return values. It covers inputs, formula, constants, use cases, and chaining. It is complete for an engineer needing to understand tool usage.

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

Parameters4/5

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

Schema coverage is 100%, so baseline is 3. The description adds the formula (I = k * dT^0.44 * A^0.725) and explains constants, which gives context beyond enum descriptions. It also notes additional output (DC resistance), adding value.

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

Purpose5/5

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

The description clearly states its purpose: 'Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula.' It specifies the resource (PCB trace width) and action (calculates), and distinguishes from siblings by suggesting chaining from voltage_divider or impedance_match.

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

Usage Guidelines4/5

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

The description provides clear context: 'Essential for power delivery, high-current motor drivers, and ensuring PCB reliability' and suggests chaining from voltage_divider or impedance_match. However, it does not explicitly exclude use cases or compare to similar tools like wire_ampacity or pcb_via_current, which are present in siblings.

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

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TDQS

A3.9/5.0

Disambiguation4/5

Despite 89 tools, each has a clearly distinct purpose with detailed descriptions that often reference related tools. Overlap exists (e.g., multiple LoRa/RF tools), but the descriptions are sufficient to distinguish them. Some confusion possible among similar-sounding tools like attenuator_pi and attenuator_tee, but the descriptions explicitly compare them.

Naming Consistency4/5

Consistent underscore-separated lowercase naming. Most tools follow a verb_noun pattern (e.g., capacitor_charge, wire_gauge) or noun_noun (power_cost). Minor inconsistencies such as 'bmi_calculator' vs 'solar_sizing' but overall predictable.

Tool Count2/5

89 tools is far too many for a single MCP server. This scope is more appropriate for multiple specialized servers. The sheer number will slow agent selection and increase cognitive load, reducing coherence.

Completeness3/5

Covers many domains (RF, solar, PCB, networking, math, etc.) but lacks depth in some areas (e.g., no three-phase power, no airflow calculations). Some domains have comprehensive coverage (LoRa/Meshtastic), but others feel incomplete for the tool count.

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