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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, so the description is free to add model-level context. It does so usefully: it names Hammerstad-Jensen (1980) thickness correction and Wheeler (1977) zero-thickness synthesis, and warns that dispersion and losses are excluded, which is a real accuracy caveat an agent cannot get from the schema.

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 sentences, both front-loaded with the operative information (what is computed, then what is returned and what is excluded). No filler, no restatement of the title.

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 usefully characterizes the return: a Wheeler zero-thickness synthesis plus a separate thickness-corrected H-J target width. The only gap is that it does not say whether the two widths are meant to be compared or which one to trust when they differ, which matters for a synthesis tool.

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%, so all five parameters (er, width_mm, height_mm, target_ohm, thickness_mm) are already documented with units and defaults. The description only indirectly gestures at thickness_mm ('thickness correction') and target_ohm ('H-J target width') without adding units, ranges, or validity constraints, so the baseline of 3 applies.

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 and resource ('Calculate microstrip impedance and effective permittivity') and pins down the exact model variants used. No sibling tool covers microstrip geometry, so there is no ambiguity about which tool to pick.

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?

Usage scope is only implied: 'dispersion and losses are ignored' tells the agent when results are invalid, but there is no explicit statement of when to choose this tool over alternatives or what inputs are required versus optional. No routing guidance is offered, which is acceptable only because no sibling is a near-duplicate.

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