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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds that the call is purely a pricing query returning a EUR amount and a minimum-file flag, which is useful, but leaves domain terms ('one check', 'minimum file') undefined and says nothing about rate limits or whether prices are cached/current.

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?

A single compact sentence with no filler, and the primary output (price in EUR) is front-loaded. Slight deduction for the awkward phrase 'one check for a number of unique phone numbers', which is harder to parse than necessary.

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 two-parameter, fully documented, read-only tool with no output schema, the description is adequate: it conveys both return components (price and minimum-file eligibility). However, business terms like 'check' and 'minimum file' are never defined, so an agent cannot fully interpret the result without guessing.

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%, with both parameters documented and an enum for service, so the schema carries the load. The description only reinforces that 'numbers' means unique numbers, which the schema's own description already states, so it adds little beyond the structured fields.

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 and output: the EUR price of checking a number of unique phone numbers, plus a minimum-file eligibility result. It is clearly a pricing/quote lookup rather than an ordering or listing tool, so it is distinguishable in intent from siblings, though it never names them.

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 explicit when-to-use or when-not-to-use guidance, and no mention of alternatives or the prerequisite that the service id must be obtained via list_services (only the schema hints at this). The agent must infer that this is a pre-purchase estimate call.

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