pcb_get_impedance_for_trace

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

The annotations already declare readOnlyHint and idempotentHint, covering the safety profile. The description adds the word 'Estimate', which provides a small behavioral hint about result accuracy, but it does not disclose any additional behaviors such as dependency on stackup configuration, potential for errors, or whether the estimate is based on specific formulas. While not contradictory, it adds minimal value beyond annotations.

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?

The description is a single clear sentence with no redundant words, making it highly concise and front-loaded. However, it is terse to the point of omitting valuable context captured in other dimensions, though that is a trade-off with conciseness rather than a flaw in structure.

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?

The tool is a simple read-only operation with a 2-parameter schema and an output schema present, which reduces the need to describe return values. However, the description lacks usage guidance, parameter semantics, and differentiation from similar siblings, making it only minimally complete for an agent to use correctly in all situations.

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?

The input schema has zero description coverage, so the description must compensate for explaining the parameters. It references 'supplied width' and 'named stackup layer', which map directly to width_mm and layer_name, but does not add meaningful semantics such as units, allowed values, or how the layer name relates to the stackup. This is insufficient to fully understand the parameters beyond their names.

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?

The description clearly identifies the action ('Estimate trace impedance') and the inputs ('supplied width on the named stackup layer'). It distinguishes the tool's scope by mentioning the stackup layer, but does not explicitly differentiate it from the sibling tool si_calculate_trace_impedance, which likely performs a similar calculation.

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 description provides no guidance on when to use this tool versus alternatives such as si_calculate_trace_impedance or si_calculate_trace_width_for_impedance. There is no mention of context, prerequisites, or exclusions, leaving the agent to infer the use case solely from the name.

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