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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely useful behavior: it is a quote that 'orders nothing', it discloses the Azure tenant-rounding rule with a note, and it points to where the exact named preview lives. It stops short of describing rate limits or response shape in detail, which keeps it below a 5.

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?

The core purpose is front-loaded in the first clause and the usage rule follows immediately; the third sentence carries real information (quote-only, Azure rounding, preview location). It is somewhat dense and longer than strictly necessary, but no sentence is filler.

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?

No output schema exists, yet the description enumerates the return content (tenants/domains, capacity, cost, delivery time) and sets expectations that names are not resolved in this tool. For a read-only pricing tool with four well-documented parameters, an agent has everything needed to call and interpret it.

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, but the description adds meaning beyond the schema: the Azure 'sold by the tenant' semantics explain why a non-filling count is quoted for whole tenants, which the enum description alone does not convey. Billing is only implied via 'monthly cost', so it does not fully round out every parameter.

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 and resource ('Prices a given number of inboxes') and immediately enumerates what the quote contains: domains/Azure tenants, daily sending capacity, monthly cost and delivery time. It also distinguishes itself from the sibling plan_infrastructure by input shape (count vs send volume).

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 when-to-use condition ('when the person already knows the count') with a concrete example, and names the alternative tool and the condition that selects it ('for a send volume use plan_infrastructure'). It further routes the user elsewhere for exact previews with real names.

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