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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so safety is covered. The description adds a genuinely new behavioral trait the annotations lack: the token cost of the unfiltered call and the scoping that avoids it. Return structure is still unspecified, but the important operational detail is disclosed.

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 short sentences, zero filler, with the resource summary first and the scoping/cost tradeoff immediately after. Every clause earns its place.

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-optional-param, no-output-schema listing tool, the description covers what is returned, the recommended filter, and the cost of not filtering. It does not spell out the shape of the returned plan objects, but that is a minor residual gap given how much it already covers.

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 100%, so the baseline is 3, and the description goes beyond the schema by explaining the practical effect of the optional 'line' parameter (all lines when omitted, at high token cost) and implicitly steering toward list_product_lines for valid ids. It adds advice the enum values alone do not convey.

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 specific verb+resource: lists plans with their prices and main features. Clearly distinct from sibling get_plan (single plan) and compare_plans, though it never explicitly names those siblings. A reader knows what it returns.

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?

Gives an explicit recommendation ('Pass line ... recommended') and states the consequence of omitting it (every plan of every line, ~10,000 tokens). It does not name alternative tools such as get_plan for a single lookup, so the routing guidance is one-sided.

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