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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is fully covered by structured data. The description adds nothing beyond that — no note that it is a pure stateless calculation, no note on how units are treated, and no mention of the result shape even though this is where such context would be cheap to include.

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?

There is zero waste, but the single fragment lacks a verb and reads as a topic label rather than a statement of function. It is under-specified rather than efficiently concise, though it is at least front-loaded with the key concept.

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?

An output schema exists, so return values need not be explained, and both parameters are documented in the schema. For a simple deterministic calculator that is close to sufficient, but the description never states the operation being performed (I_branch = I_total × R_other / R_sum) or unit expectations, leaving the agent to reconstruct intent from the name and sibling list.

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 both parameters (resistors, total_current) carry their own descriptions and examples, so the schema does the heavy lifting. The description's phrase 'parallel resistors' reinforces that the array items are branch resistances but adds no format, unit, or ordering detail beyond the schema. Baseline 3 applies.

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 fragment names a specific electrical quantity (branch currents) in a specific context (parallel resistors), which is enough to infer the current-divider formula. But it is a noun phrase with no verb, and it never distinguishes itself from related siblings such as calculator_parallel_resistance, calculator_series_resistance, or calculator_voltage_divider.

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?

There is no guidance whatsoever on when to reach for this tool versus the many nearby resistance/current/voltage calculators. The agent must infer from the name alone that this computes per-branch current rather than total resistance or a voltage drop.

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