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 goes further and discloses the actual algorithm (design amps = load × 1.25 if continuous, smallest AWG above design amps, 240.4(D) cap, iterative step-up for voltage drop). It does not state what the response contains (gauge, breaker size, drop %, pass/fail), and there is no output schema to fill that gap.

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?

Front-loaded with the outcome, then the governing formulas; nothing is decorative. The second sentence is very dense with notation but each clause maps to a distinct parameter behavior, so it earns its space for an engineering calculator.

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 9-parameter, fully-optional calculator with no output schema, the description explains the computation chain end to end, including the temperature-column and small-conductor nuances an agent could not infer. The one meaningful omission is what results are returned (final gauge vs. breaker size vs. drop percentage).

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 the baseline is 3; the description adds real conceptual meaning by tying terminal_c to temperature columns, continuous to the 125% multiplier, and one_way_ft to the voltage-drop formula with its K constants (12.9 copper, 21.2 aluminum) and √3 three-phase factor. This exceeds mere restatement of 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?

States a concrete outcome ("What gauge wire you need for a circuit") and the specific inputs it consumes (copper/aluminum, NEC ampacity table, temperature column, 125% rule, 240.4(D) small-conductor cap). The verb+resource is unambiguous, but it does not name or differentiate itself from the sibling calc_voltage_drop, even though it embeds voltage-drop math that sibling also covers.

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 is implied rather than stated: "optional voltage-drop check for long runs" hints at when the drop path matters, and the schema's "0 = skip voltage drop" clarifies the trigger. However, there is no explicit when-to-use/when-not guidance and no routing to calc_voltage_drop for pure drop calculations.

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