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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real value beyond that: it discloses the server-side derivation of inputs and that the engine is the Phase-25 implementation behind POST /api/pdn/analyze. It does not cover failure modes or runtime characteristics, but that is a minor gap given the annotation coverage.

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?

Three tight sentences, front-loaded with the purpose and outputs before the derivation and no-arg usage note. The internal engine/endpoint reference is slightly implementation-flavored but short enough to earn its place.

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 enumerates what the analysis returns, and it explains that all four optional parameters are derived server-side. Combined with 100% schema coverage and read-only annotations, this is nearly complete, with only return format/pagination left 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%, and each parameter's schema already documents its 'derived when omitted' behavior, so the description largely repeats structured data. It reinforces the no-argument default but adds no syntax or format detail beyond the schema, making the baseline 3 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 and resource (PDN impedance analysis) and enumerates the concrete outputs: interplanar capacitance, decoupling impedance vs. target, violations, and recommended caps. It is clearly distinguishable from sibling analysis tools like run_stackup_solver and run_thermal_analysis by domain and by the enumerated results.

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?

Gives a clear precondition ('call with no arguments once a design exists') and explains that all inputs are derived server-side, which tells the agent when the tool is applicable. It stops short of naming an alternative or stating when not to use it, so it is strong context rather than full routing guidance.

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