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

Annotations already cover read-only / non-destructive / closed-world, so the description's value-add is the computation disclosure and the 'partial answer says it is partial' behavior, which tells the agent how incomplete inputs are surfaced. It does not describe output shape or rounding/units, keeping it short of a 5.

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?

Two sentences, no filler, and the computation detail is front-loaded after the core purpose. The second sentence is long and clause-stacked but each clause (amortization, cost components, partial disclosure) carries real 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?

For a 12-parameter calculator with no output schema and zero required parameters, the description should indicate the minimum viable input set and what the result contains. It explains the formula and partial-result behavior but leaves the agent guessing which inputs are mandatory and what the returned comparison 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 description coverage is only 8% across 12 parameters, so the description must compensate. It names purchase price, years kept, resale, insurance, maintenance, fuel and driver pay conceptually, but never explains mpg, miles_per_year, trips_per_year, driver_hours_per_year, or how trips_per_year interacts with alternatives whose unit is 'trip' vs 'month'.

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 states a concrete computation: yearly cost of owning a bus versus charter, contracted shuttle, or rideshare. That is a specific verb+resource and is clearly distinguishable from the sibling retrieval tools (get_used_bus_prices, search_buses). It stops short of explicitly saying how it relates to those siblings as data sources, so not a 5.

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?

Usage is only implied: 'using only figures the caller supplies' hints that the agent must gather inputs first, and the partial-answer clause hints at degraded calls. There is no explicit statement of when to reach for this vs. get_used_bus_prices or get_buying_context, nor which inputs are needed for a meaningful comparison.

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