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

Annotations already cover the read-only and closed-world profile, and the description adds real value on top: it discloses the return shape (cheapest plan, reasons, up to 3 alternatives, source links) and honestly flags that the 'usage' rule is a labeled rule of thumb rather than authoritative. It stops short of noting what happens when no plan fits the budget or how fresh the pricing data is.

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 outcome, then a compact parameter glossary; no filler sentences. The pipe-delimited value lists are dense but readable, and nothing redundant is repeated.

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 explains the return payload, and all four parameters are documented. The remaining gaps are the no-fit/budget-exceeded behavior and any relationship to the sibling recommendation tools.

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% and the schema carries no enums, so the description is the only source of meaning — and it delivers all four: interface (terminal | ide | any), budget_usd (monthly USD), usage (light | daily | heavy), who (individual | team). That is a full compensation for the coverage gap.

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?

The description gives a specific verb and resource ('returns the cheapest fitting plan') plus the exact output payload (reasons, up to 3 alternatives, source links), and anchors it to a known public tool. It does not, however, distinguish itself from the sibling 'recommend_plan', which sounds near-identical in purpose.

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?

There is no when-to-use guidance and no exclusions. With siblings named 'recommend_plan', 'list_plans', 'get_tool_plans' and 'route_task', the agent is left to guess which one to call; the description never mentions an alternative or a triggering condition.

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