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

Annotations already cover read-only, idempotent, non-destructive behavior, so the burden is light. The description adds real context beyond that: the cost breakdown it computes, the suggested selling price, and the default assumption values an agent should know before overriding them.

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 tight sentences: the first names what is computed, the second the inputs and defaults. No wasted words and the key requirement (weight and time) is front-loaded.

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?

With 13 parameters but only 2 required and a light annotation profile, the description gives the agent enough to call it correctly: required inputs, default assumptions, and the output concept. No output schema exists, but the description names the returned cost and selling price, which is sufficient for a calculator.

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 only 46% across 13 parameters, so the description must compensate, and it does for the most important ones by spelling out defaults (1 kg spool at $20, 120 W, $0.12/kWh, 5% failures) and framing the two required inputs as slicer outputs. It leaves a few params (quantity, markup, printer lifespan) implicit, keeping it from a 5.

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 ("Estimate") and resource ("what an FDM print costs") plus the exact cost components and the derived selling price. Clearly distinct 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 prerequisites clearly: the two required inputs come from the slicer and everything else is optional with defaults, which tells the agent how to call it minimally. It does not name alternatives or when-not-to-use cases, so it stops short of a 5.

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