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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely non-structured behavior: results are sorted cheapest first, the payload includes input/output prices, a blended 3:1 figure, context size, supported features, rate-limit docs, and that units appear in the result.

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?

It is a single run-on sentence built from stacked parentheticals, which makes it hard to parse and pushes the key mode distinction (models vs. unit-based tool prices) into the middle. The information is compact but not front-loaded or structured.

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 must carry return-value burden, and it does list the returned fields, the sort order, and that units are echoed in the result. Only the exact response shape and error/empty-result behavior remain unspecified.

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 both parameters are already documented and a 3 would be the baseline. The description adds meaning beyond the schema by defining the 'blended 3:1' ratio and clarifying that an empty unit means model tokens while a unit value switches to per-call tool pricing.

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 identifies the resource (model token prices per million, or per-call prices for tools when a unit is set) and the ordering (cheapest first), so an agent can infer this is a pricing lookup. However it is a verbless noun phrase with no explicit statement of what the tool does, and it never differentiates itself from siblings like compare_tools or get_tool.

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 'or with unit set ... per-call prices for tools' clause implies the two modes (models vs. tools) and thereby when to supply a unit, but this is only implied. There are no explicit when-to-use/when-not statements and no mention of when to prefer compare_tools or get_tool instead.

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