impedance_calc

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

Annotations already cover the safety profile (read-only, idempotent, non-destructive), so the description's real contribution is accuracy disclosure: closed forms are ~10% optimistic for tightly coupled pairs, and the tool reports the fab's own published number when geometry matches a table entry. That is genuine behavioral context beyond the annotations, though it omits any formatting/units caveat for the returned value.

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 tightly written sentences, front-loaded with what it does, followed by the accuracy caveat and design recommendation. No filler, no repetition of schema or annotation content.

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 an output schema present, return values need no explanation, and the read-only annotations cover the safety profile. What remains for the agent to know — method, accuracy limits, which result to trust, and where presets are defined — is all supplied.

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 coverage is 100%, so 3 is the baseline; the description exceeds it by scoping the computation to outer-layer geometry and framing "pair" vs. single-ended, which maps meaningfully onto the gap_mm distinction. It adds no syntax details beyond the schema, but the applicability constraint is real added meaning.

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?

Specific verb+resource combo ("Estimate the impedance of an outer-layer trace or pair on a stack-up preset") that no sibling covers, and it names the two computation paths (closed-form microstrip formulas vs. the fab's published table entry). An agent can distinguish it from stackup_info, review_board, etc. without opening a schema.

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 gives decision guidance: use the closed-form result generally, but design to the table entry when the geometry matches. It also references stackup_info for preset definitions. It lacks an explicit "when not to use this" exclusion, but the context is clear enough to invoke correctly.

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