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

Annotations cover read-only/idempotent safety, and the description adds genuinely non-structured context: the tool is members-only, costs $0.50 per calculation in USDC via x402 with no free allowance, and a 50-item list bills per item. This is exactly the kind of payment/auth disclosure annotations can't carry, though return format details (units, rounding) remain unstated.

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?

Purpose and cost are front-loaded, which is good, but the body is a dense run-on packed with parentheticals that duplicates the schema and is hard to parse. Several clauses repeat the nested input definition verbatim from the schema.

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 nested-object tool with no output schema, the description does explain what the calculation returns (losses, present cost, payback, with formula and source) and discloses payment terms. The main gap is the ambiguous sentence/spec/design/items alternation, which isn't fully clarified.

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 schema already documents every parameter including the nested input fields. The description largely restates that same input text (amps, hours, mu, price, years, interest, lengthM, ambientC, freq, extra) rather than adding new semantics, so it sits at the baseline.

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 computation (economic size of an MV/HV design via IEC 60287-3-2) and enumerates the outputs: energy lost per year for this size and one/two sizes up, present cost, and discounted payback. It's clearly distinguishable from siblings like design_cable, though it doesn't explicitly announce that distinction beyond referencing 'as design_cable takes it'.

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 through the input contract and the sentence/spec/design/items alternatives, but there is no explicit statement of when to choose this tool over design_cable or mv_electrical, nor of prerequisites or exclusions. The 'Always paid' note hints at a gating condition but doesn't frame tool selection.

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