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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior. Beyond that, the description adds genuinely useful behavior: it will not interpolate between published price steps and returns a range instead, and it explicitly reports when price rules are absent. Those are non-obvious response behaviors that the annotations do not cover.

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?

Three tight sentences, front-loaded with the core purpose, then return contents, then scope and the range caveat. Dense but no filler; every clause carries 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 7-parameter, 0%-coverage schema with no output schema, the description usefully explains the return shape and price-rule caveat. It still leaves two parameters (plan_id, include_personal) and the exact units semantics undocumented, which is a real gap given that no structured field compensates.

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 0%, so the description carries the burden. It meaningfully maps units ('team size, or companies/orders per the product's axis') and billing ('monthly or annual'), and mentions usage and add-ons implicitly. But plan_id and include_personal are never explained, and the meaning of the axis-switching for 'units' is left vague.

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+resource ('Cost of each plan at a team size') and enumerates the return contents (monthly equivalent, amount billed per period, commitment, minimums, add-ons, usage). It also scopes itself ('Only for products with price rules'). However, it never names or contrasts with siblings like compare_offer_costs or cost_at_growth, so an agent must infer the boundary itself.

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 scoping clause 'Only for products with price rules; says so otherwise' gives one real usage condition, which is better than nothing. But there is no explicit when-to-use guidance or routing to alternatives such as compare_offer_costs or cost_at_growth, leaving the agent to guess when estimation vs comparison is appropriate.

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