Utility (freely callable)

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context: it auto-detects the mode based on provided parameters and lists the specific parameter combinations for each mode. This goes beyond the schema and annotations by explaining the tool's operating logic, though it could further detail what computed geometry includes or how hints are derived.

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?

The description is well-structured and concise. It leads with the purpose, then uses a bulleted list to specify auto-detect modes, followed by usage guidance and a note on free callability. Every sentence adds value, and the formatting improves scannability. There is no redundancy or fluff.

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?

Given the tool's complexity (8 optional parameters, multiple modes), the description provides complete context: what it computes, how to use it, when to use it, and that it is freely callable. The output schema exists, so return values are documented elsewhere. The description fully compensates for the ambiguity caused by having no required parameters and multiple modes.

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 each parameter. The description adds significant meaning by explaining how parameters interact: rim mode, tire mode, hf_tire mode, and package mode. For example, it clarifies that section_width is in mm for metric tires but inches for HF tires, and that rim_offset is optional. This mode logic is essential for correct invocation and is not fully captured in the schema.

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 clearly states the tool's function: 'Get computed geometry, population stats, and hints for a wheel/tire spec.' This is a specific verb+resource with clear scope. It distinguishes itself from sibling search/check tools by explicitly positioning it as a pre-processing utility, and the auto-detected modes further clarify its unique role.

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 description explicitly states when to use the tool: 'Use before search or classified calls to understand whether a spec is common or unusual, what tolerances to use, and what to expect.' It also notes it can be called freely without user initiation, which is a clear usage guideline. This is highly actionable and distinguishes it from sibling tools that perform searches or fitment checks.

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