list_phones

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

With no annotations, the description carries the full burden. It does disclose the authentication requirement and the need to retry after establishing a session, which is useful. However, it does not mention return format, pagination, or whether only verified/primary numbers are included, leaving some behavioral gaps.

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 compact and front-loaded with the core purpose, followed by a clearly labeled ACCESS note. Every sentence earns its place, and the structure makes the authentication requirement stand out without bloating the description.

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 zero-parameter read-only list tool, the description covers the essential context: what is listed, the scope, and how to authenticate. The absence of an output schema is somewhat mitigated by the clear scope, though a note on the response shape would make it fully complete.

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 accepts zero parameters, so there are no parameter semantics to document. The description appropriately focuses on what is returned rather than input details, and the baseline for zero-parameter tools is respected.

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 ('List') and resource ('all phone numbers associated with the authenticated account'), making the tool's scope immediately clear. It also differentiates from sibling phone-related operations like remove_phone and set_primary_phone by focusing purely on listing.

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 ACCESS section clearly explains the prerequisite: a Proof account, and gives two concrete ways to satisfy it (set PROOF_API_KEY or use start_login). It does not explicitly contrast with alternative list tools, but the context and resource make appropriate usage obvious.

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