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

Annotations already declare the tool as read-only, idempotent, and closed-world, so the safety profile is covered. The description adds an example of the output but no behavioral context beyond what the annotations provide, such as output format or edge-case behavior.

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 front-loaded with a helpful example, followed by a compact capability statement, and ends with a URL. It is appropriately sized, though the URL is non-essential for tool invocation.

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 nine optional parameters with full schema coverage and no output schema, the description supplies a concrete example of the returned value and covers the core features (units, split, round trip). It leaves minor ambiguities, such as whether the output is total or per-person, but is otherwise complete enough 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 description coverage is 100%, so all nine parameters are self-documented. The description loosely maps some parameters to real-world meaning (economy units, cost splitting, round trip) but is largely redundant with the schema and does not add syntax or format details beyond it.

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 uses a specific verb ('Price') and resource ('one-way or round trip') and illustrates with a concrete example, making the calculation purpose clear. It does not explicitly name or distinguish itself from the sibling fuel_economy_converter, so it falls short of full sibling differentiation.

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 states what the tool can compute but gives no explicit when-to-use guidance, no prerequisites, and no mention of alternatives such as fuel_economy_converter. It is a capability statement rather than usage direction.

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