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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety behavior is fully covered. The description adds value by disclosing what the returned data actually contains (per-inbox send pace, delivery time, all billing cycles), going beyond what the annotations say. It stops short of describing format or whether pricing is static, which keeps it at a 4.

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 sentences: the first front-loads what the data is and what dimensions it covers, the second routes to the alternative. Nothing is wasted, and the enumeration of providers and fields earns its space by telling the agent what it will get.

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 parameters and no output schema, the description carries the burden of explaining the return content, and it does so by listing the axes of the price list. Minor gaps remain (currency, unit of pricing, whether tiers are returned as a table), but nothing prevents a correct call.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies a no-argument, whole-catalog read.

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 names a specific resource (the WarmInboxes price list as data) and enumerates its scope: prewarmed/fresh inboxes across Google Workspace, Microsoft 365 and Azure, billing cycles, safe daily send pace, and delivery time. It also explicitly distinguishes itself from plan_infrastructure, so an agent can tell the two apart without inspecting 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?

It gives an explicit routing rule — use plan_infrastructure when you need a costed fleet for a volume — which is exactly the when-not guidance that matters for a catalog lookup. It does not mention the other closely related sibling, quote_inboxes, so the guidance is clear but not exhaustive.

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