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

Annotations already cover the safety profile (readOnlyHint=false, openWorldHint=true, destructiveHint=false), and the description adds genuinely non-structured context: per-call credit costs (IP 1, signup up to 3) and that demo fixtures consume no credits. It stops short of stating auth requirements, rate limits, or whether the response is cached/idempotent despite idempotentHint=false and an idempotency_key parameter.

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?

Three short sentences, front-loaded with purpose then return value then cost, with no filler. The credit sentence mixes in phone/email pricing irrelevant to this tool, which slightly muddies an otherwise tight statement.

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 3-parameter, no-output-schema tool, the description covers purpose and cost but leaves the return shape ('signals and a summary') undefined and two optional parameters unexplained. An agent can call it with just an IP, but cannot confidently use country scoping or idempotency 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 description coverage is 0% — none of the three parameters have descriptions, and the description text never mentions 'country' or 'idempotency_key' at all. Only the required 'ip' is implicitly explained by the tool name, so the description fails to compensate for the undocumented optional parameters.

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+resource ('Check ip') and the intended outcome ('signup or lead-list quality'), plus what comes back ('signals and a summary'). It is clear what the tool does, but it never names or contrasts the siblings check_email/check_phone/check_signup, so the agent must infer routing from the resource noun alone.

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?

'for signup or lead-list quality' implies the use case, and the credit line hints this is a metered call, but there is no explicit when-to-use, when-not-to-use, or alternative routing to check_signup vs check_ip. Usage is only inferable, not stated.

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