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

Annotations already declare readOnly/idempotent/non-destructive, so the description is free to add real behavioral context: the estimate is geometry-only, feature-blind to holes and corner radii, and capped at 60,000 triangles. That's exactly the kind of expectation-setting an agent needs. It stops short of saying whether the pricing block changes the return shape.

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?

Three tight sentences: capability first, then limitation, then input cap. No filler. Slightly dense in the first sentence's output list, but every clause carries information.

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 no output schema, the description does a decent job naming what comes back, but for an 8-parameter tool with a nested pricing object and quantity/setups concepts, it leaves the agent guessing how quantity or pricing extras affect the answer and what the numeric result looks like.

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 50%, and the description only gestures at parameters indirectly ('stock block' hinting at allowance_mm, 'material removal rates given' hinting at the material object). Units, defaults, and defaults for up/setups/quantity/machine_rate_per_hour are left entirely to the schema, so it neither compensates nor is required to.

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+resource ('Budget estimate for machining a part from an STL') and enumerates the computed outputs (stock block, material removed, surface area, roughing/finishing time, mass). It implicitly separates itself from the DXF and g-code siblings by working on STL geometry, but never names those alternatives.

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?

The 'Based on volume and surface area only; holes and corner radii are not detected' clause is a useful applicability caveat, and 'before CAM' in the title nudges timing. However there is no explicit routing to analyse_dxf_for_cutting for 2D parts or estimate_gcode_run_time for exact CAM time, so when-to-use is only implied.

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