list_phone_numbers

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool lists phone numbers and returns a list, but lacks details on permissions required, rate limits, pagination, or error conditions. For a read operation with zero annotation coverage, this is a significant gap in transparency about how the tool behaves beyond its basic function.

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 extremely concise and front-loaded: it states the purpose in the first clause, the return value in the second, and usage guidelines in the third. Every sentence adds value without redundancy, making it efficient and easy to parse for an AI agent.

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?

Given the tool's low complexity (0 parameters, no output schema, no annotations), the description covers the basics: what it does and when to use it. However, it lacks details on return format (e.g., structure of the 'phone number list'), error handling, or any behavioral constraints. For a simple list tool, this is minimally adequate but leaves gaps an agent might need to infer.

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 tool has 0 parameters, and schema description coverage is 100% (though empty). The description doesn't need to explain parameters, so it appropriately focuses on the tool's purpose and usage. No parameter information is missing or needed, making this adequate for a parameterless tool.

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 clearly states the action ('Lists') and resource ('account phone numbers'), making the purpose immediately understandable. It distinguishes itself from siblings like 'make_outbound_call' or 'get_voice' by focusing on listing phone numbers rather than using them or managing other resources. However, it doesn't explicitly differentiate from potential similar listing tools (though none exist in the sibling list).

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 provides clear context for when to use this tool: 'viewing available numbers for outbound calls.' This gives the agent a specific scenario for invocation. It doesn't explicitly state when NOT to use it or name alternatives, but the context is sufficient for basic guidance given the tool's straightforward nature.

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