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

Annotations already cover read-only/idempotent/non-destructive, and the description adds real context on top: a cap of three results, what each brand entry contains (cheapest qualifying model, seat label, dated price, source), explicit caveats that seat labels are the seller's and that electrical fit and delivery are unconfirmed, and the trust signal that sponsorship does not affect selection.

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?

Front-loaded with the action and inputs, then the result shape, then caveats — a sensible order with no filler. The middle sentence is long and packs several clauses together, which costs a little readability.

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 correctly spends words on what comes back (price sources, tradeoffs, checks still needed) and on what is explicitly not validated. It does not say what happens when nothing matches or whether results can be fewer than three, a minor remaining gap.

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 50% (heatType and placement enums are undocumented), and the description compensates by clarifying the budget as 'sauna-only USD' and by explaining the non-obvious semantics of `people` — that each brand surfaces its cheapest model rated for at least that many people. The enum values themselves are still unexplained, though they are largely self-evident.

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?

States a concrete verb and resource ('Shortlist up to three sauna brands') plus the exact inputs used for selection, so the agent knows this is a filtered shortlist generator rather than a comparison or quoting tool. It never names compare_sauna_brands, so the boundary with that sibling is inferred from 'shortlist up to three' rather than stated.

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?

'No contact details required' clearly positions this as the early-research step before prepare_sauna_quote_request / submit_sauna_quote_request, and 'checks still needed' signals it is not a final quote. However, no sibling is named and no explicit 'use X instead when' routing is given.

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