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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral context beyond that: what the computation includes (failure allowance, machine wear) and which defaults are applied (1 kg spool at $20, 120 W, $0.12/kWh, 5% failures), which tells the agent the output is deterministic and assumption-driven.

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?

Two dense sentences, front-loaded with the purpose and followed by the input requirements and default assumptions. No filler, though the parenthetical cost-component list is somewhat long.

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 13-parameter tool with no output schema and low schema coverage, the description covers the essentials (what it computes, required inputs, key defaults) but omits the remaining parameters and gives no indication of the shape of the returned cost/selling-price breakdown. Adequate but with visible gaps.

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 only 38% across 13 parameters. The description usefully explains the roles of the required weight/time inputs and enumerates key default values (spool price, printer power, electricity rate, failure rate), compensating partially. But it leaves quantity, markup_percent, printer_cost_usd, lifespan, and labor_rate undocumented in either place.

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?

Specific verb ('Estimate') and resource ('FDM print costs'), with an explicit breakdown of the cost components (material, electricity, machine wear, labor, failure allowance) plus selling price. This clearly distinguishes it from siblings like calculate_filament_usage or calculate_volumetric_flow, which compute a single quantity rather than a full cost model.

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?

Explains the context of use by naming the two required slicer-derived inputs and reassuring that everything else defaults sensibly. It does not, however, explicitly route the agent away from sibling calculators or state when a cost estimate is preferred over a filament estimate.

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