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

Annotations declare readOnlyHint=true, but the description says the designed gain is auto-applied to the chain's antennaGainDbi unless apply_gain=false — a state mutation. That directly contradicts the read-only annotation. The description is otherwise candid about side effects, but the conflict with the annotation triggers a 1 under the rubric.

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?

A single dense paragraph that front-loads what is designed, then the model, then the default behaviors and return contents. Every clause carries information, though the substrate/gain sentences could be broken out for faster scanning.

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?

For a 14-parameter tool with no output schema, the description covers the substrate sourcing logic, the array conditional, the auto-apply side effect, and enumerates return contents (dimensions, resonance/bandwidth/gain, beamwidths, pattern cuts, grating-lobe check). Remaining parameter specifics are fully covered by the schema.

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 already 100%, so the baseline is 3, but the description adds real meaning: the substrate defaulting rule, the array-vs-single conditional on nx/ny, and the note that omitting user_request labels results 'caller-asserted'. The material-resolution guidance is also reinforced rather than merely restated.

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+resource (design a rectangular microstrip patch antenna / planar array), names the underlying model (Balanis cavity + array factor), and ties itself to a concrete endpoint and UI panel. An agent can distinguish it from design_rf_chain or run_stackup_solver without opening the 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?

Gives clear conditions: array mode triggers only when both nx and ny are supplied, and substrate values derive from the latest solved stackup unless dk/df/h_mm are given explicitly. It does not, however, name when to prefer a sibling tool (e.g. design_rf_chain vs this) or state exclusions.

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