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

With readOnlyHint=true already covering safety, the description still adds real behavioral context: defaults for tolerance/trace width, frequency derivation from the solved stackup, the differential-pair tolerance halving, and the caller-asserted vs verified labelling consequence of omitting user_request. The Phase-24/POST endpoint reference is implementation detail rather than agent-relevant behavior, keeping it out of the top score.

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 purpose and ranking logic are front-loaded in the first sentence, and the calling guidance follows. The third sentence on the Phase-24 engine and internal POST route is low-value for an agent deciding whether to call, marginally diluting otherwise efficient prose.

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?

No output schema exists, and the description compensates functionally by explaining that results are ranked styles with the cheapest qualifying one marked. Combined with full parameter coverage and read-only annotations, an agent has enough to invoke correctly; only the exact result shape remains unspecified.

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 the five parameters and their defaults are already fully documented in the schema; the baseline is 3. The description largely restates those same defaults (tolerance 5%, trace width 0.1, derivation when omitted) without adding syntax or format detail beyond the schema.

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 names a specific verb ('Recommend') and resource ('PCB glass-weave (fiber-weave) styles') and states the scope precisely: ranks catalogued styles by impedance variation and cost for the design frequency, and marks the cheapest one meeting the tolerance. This is distinguishable from every sibling analysis tool at a glance.

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?

It gives a concrete precondition and calling pattern -- 'call with no arguments once a design exists' -- plus which inputs are derived vs defaulted. It does not name a specific sibling or state exclusions (e.g. that a solved stackup must exist first), so it falls short of explicit alternative routing.

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