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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: it discloses the derivation logic (pool sized from trip length), the exact three-tier output with multipliers, the per-option payload (pool GB, price, reason, buy_url), budget marking, and price parity with quote_route.

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 dense sentences with the trigger condition front-loaded and zero filler; every clause (sizing basis, multipliers, per-option fields, budget check, price parity) carries decision-relevant 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 an eight-parameter read-only recommender with no output schema, the description supplies the missing return-value picture (three tiers, their contents, buy_url, budget flags) and the sizing rule, leaving nothing an agent needs before calling.

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 eight parameters are already documented, including usage→GB/day mapping and the gb_per_day-wins-over-usage rule. The description only restates the country/days/usage inputs at a high level and adds no syntax or precedence detail beyond the schema, so baseline 3 applies.

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?

Specific verb and resource: it sizes a shared data pool from a described trip and returns three server-quoted routes (exact, ×1.5, ×2). It explicitly differentiates itself from the sibling quote_route by the input framing ('trip instead of a size'), so an agent can pick it without opening either schema.

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 first clause is an explicit selection rule ('Use when the customer describes a trip instead of a size') with the inverse condition implied, and it names quote_route to explain the price relationship so the agent knows which sibling to call for a size-based request.

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