list_available_phone_numbers

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

No annotations are provided, so the description must bear the full transparency burden. It implies a read-only listing action through the words 'List' and 'Browse', and mentions the 'limit: Max results' behavior. However, it does not explicitly state that no side effects occur (e.g., it does not purchase or reserve numbers), though 'before buying' partially conveys this.

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 concise and front-loaded with the main purpose. The Args section is clearly formatted, each element contributing useful information without redundant elaboration. Every sentence earns its place.

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 simple listing tool, the description covers the purpose, usage context, and key parameter details. Since an output schema exists, there is no need to describe return values. Minor gaps like pagination behavior beyond the limit are not critical for this tool's use.

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%, so the description compensates by explaining each parameter: type as 'TollFree' (default) or 'Local', country as 'Two-letter country code', and limit as 'Max results'. This adds meaning beyond the schema, which only provides titles and defaults.

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 'List available phone numbers to purchase' with a specific verb and resource, clearly indicating the tool's purpose. It distinguishes itself from the sibling 'list_phone_numbers' by specifying these are numbers available for purchase, and also names 'provision_phone_number' as the related next step.

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 gives clear context: 'Browse numbers before buying with provision_phone_number' implies this is the pre-purchase exploration step, contrasting with provisioning. It does not explicitly state when not to use it, but the purpose is unambiguous enough to guide the agent.

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