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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile needs no restatement. The description adds the shape of the result (cheapest fitting plan per size, plus plan-change breakpoints), which is useful since no output schema exists, but it says nothing about assumptions, defaults, or how the computation is bounded.

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?

A single tight sentence with zero filler, front-loaded on the core behavior and then the secondary output (breakpoints). Nothing repeats the tool name or annotations.

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 three-parameter analytical tool with no output schema and zero parameter documentation, the description covers the conceptual output but leaves the inputs and usage context for the agent to guess. Adequate as a one-line summary, insufficient to invoke confidently.

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% across three parameters, so the description carries the full burden. 'At each size' loosely hints that points are team sizes, but billing (annual vs monthly) and product_id are left completely undefined, and the default annual billing is unmentioned.

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 computation: cost across team sizes plus the crossover points where the best plan changes. The 'as a team grows' framing distinguishes it from siblings like estimate_cost or compare_offer_costs, which are single-point comparisons. It stops short of naming an alternative explicitly, so it is clear but not sibling-differentiating by name.

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 — an agent can infer this is for growth-curve questions rather than a one-off cost estimate. There is no when-to-use statement, no stated prerequisites, and no pointer to estimate_cost or compare_offer_costs for simpler cases.

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