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

Adds a genuinely useful trait beyond the annotations: 'Live numbers are billed monthly each' warns of recurring cost, which matters for a destructive, open-world purchase. It still omits what happens if fewer than the requested quantity are available, whether the call is partial-success, and what permissions are needed — though annotations already flag destructiveHint=true.

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?

Two sentences, zero filler, with the bulk/area-code scope front-loaded and the billing caveat second. Nothing could be removed without losing information.

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 destructive, open-world purchase tool with no output schema and 40% param coverage, key gaps remain: which numbers were actually purchased in the response, behavior when inventory is insufficient, and the 1–50 quantity bound. The cost warning is a good start but the definition is not fully self-sufficient.

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 only 40%, so the description must compensate. It clarifies the semantics of area_code (single area code for the whole batch) and quantity (multiple numbers), and its 'sender pool' example hints at pool_id, but tags and the 50-cap are left to the schema and pool_id is only echoed implicitly.

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 (buy several numbers) with a scope qualifier (in one area code, at once), which implicitly distinguishes it from the single-number sibling purchase_number. It never names that sibling, so the differentiation is inferential rather than explicit.

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 parenthetical '(e.g. for a sender pool)' gives one concrete context, implying bulk provisioning use. It does not say when to prefer purchase_number instead, nor that inventory should come from search_available_numbers first, nor any prerequisite about registration/verification.

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