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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, and destructiveHint=false. The description adds substantial context beyond annotations: OAuth or tpsc_live_ key auth, credit consumption per check, double cost for US numbers, free checks for non-mobiles and invalid numbers, and API equivalence to POST /v1/dead-number.

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 three tight sentences, front-loaded with purpose and followed by auth and billing details. Every sentence adds useful information with no wasted wording.

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 output schema, the description still explains the result categories, authentication requirements, billing behavior, and API equivalence. That is sufficient for an agent to understand and invoke the tool correctly.

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 single phone_numbers parameter is fully documented in the schema, including the 500-number limit and example format. The description adds cost semantics tied to number type and US status, which helps interpret the parameter values, though it does not add format details beyond the schema.

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 states a specific verb and resource: live mobile network (HLR) lookups, with outcomes live, switched off, or dead. It is clear what the tool does, but it does not explicitly distinguish itself from siblings such as screen_numbers or wash_au_numbers.

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?

The description implies usage for checking whether mobiles are live and notes the live-account requirement. However, it gives no explicit when-to-use guidance versus alternatives and no when-not-to-use exclusions.

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