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

Annotations already cover read-only, idempotent, non-destructive behavior, but the description adds meaningful calculation traits: sequential waterfall processing, unknowns cascading, every order compared, and default 'typical figures for three verifiers' when no custom rates are supplied. It stops short of describing the exact response shape or the assumptions behind those typical figures, so it is not 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 description is two sentences, front-loads the purpose, and each clause adds concrete information: process, comparison, optimization objective, default, and override. No 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?

For a read-only pricing tool with a fully described schema and safety annotations, the description supplies enough to call the tool and understand its optimization objective. Because there is no output schema, it could more explicitly describe the returned comparison format beyond 'cheapest cost per usable email first.'

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 listSize and the verifier fields are already documented in the schema. The description adds the important default behavior—three typical verifiers are used unless the caller passes custom prices and resolve rates—though the parenthetical 'POST JSON for verifiers' is a little unclear and listSize is not discussed.

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 opens with a specific verb and resource: 'Price an email verification waterfall.' It then clarifies the mechanics (sequential verifiers, unknowns passed down, every order compared) and the optimization goal (cheapest cost per usable email), so an agent can tell it is a pricing/planning tool rather than a direct verification tool like verify_email.

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 implied by the opening 'Price...' scenario, but the description never states when to choose this over verify_email or quote_inboxes, nor any when-not conditions. The only conditional guidance concerns supplying custom verifier data, which is parameter usage rather than tool-selection guidance.

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