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

Annotations already establish the read-only, non-destructive profile, so the bar is lower. The description still adds meaningful context: output is source-attributed published guidance plus a test method, and it proactively discloses a limitation ('no single universal hole offset, because none is published'), which prevents the agent from overpromising.

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 sentences, zero waste, and the usage trigger is front-loaded ahead of the return and limitation notes. Every sentence carries a distinct piece of 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 an output schema present, the description need not explain return values, and it still covers usage trigger, output nature, and an explicit limitation. Nothing an agent needs to select or call the tool correctly is missing.

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%, so the schema already documents fit_type, hole_axis and hole_diameter_mm. The description's scenario list loosely maps to the fit_type enum values but adds no format or syntax detail beyond the schema, matching the baseline 3.

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 description pairs a specific verb and resource ('size a printed hole or fit') with an enumeration of the exact scenarios it handles (sliding, bolt/pin clearance, mating, press, snap). It also states plainly what it returns (published starting clearances and hole guidance with sources), letting an agent distinguish it from generic siblings like get_design_guidance.

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?

It gives an explicit usage trigger ('Use this when someone asks what clearance or hole size to draw') followed by concrete scenario examples. It does not name alternatives such as get_design_guidance or state when-not-to-use, so it stops short of a full routing rule.

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