calculate_trace_impedance

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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description usefully adds the computational method (IPC-2141 / Wheeler, 'exact' solve), but says nothing about assumptions, validity ranges, or what is returned. Adequate but thin beyond the structured fields.

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

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

Two dense sentences with no waste: purpose and method first, then the design use cases. Every clause earns its place and nothing is buried.

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

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

With no output schema, the description compensates by stating the tool solves for trace width W and spacing S for a target impedance, giving the agent a sense of the return. It stops short of documenting output units, validity limits, or solver failures.

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

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

Schema description coverage is 100%, including enum and defaults for mode, target_z, gap, Er, dielectric height and copper thickness, so the schema carries the parameter burden. The description adds only a high-level mapping to target impedances already exemplified in the schema – baseline 3 is appropriate.

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

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

States a specific verb (calculate) and resource (characteristic/differential impedance for PCB microstrip traces), and names the governing method (IPC-2141 / Wheeler). However, it never distinguishes itself from close siblings such as calculate_pcb_stackup_impedance or analyze_impedance_tolerance, so the agent must infer the boundary.

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

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

The examples (50Ω RF, 90Ω USB, 120Ω RS485/CAN) imply the design-time scenario, and the description notes it solves for width/spacing from a target impedance. But there is no explicit when-not-to-use or named alternative among the many impedance-related siblings, leaving routing to inference.

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