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

With no annotations provided, the description carries the full disclosure burden. It discloses the access-control behavior (requires authentication) and the workflow detail that start_login 'opens this tool,' which is genuinely useful beyond what the name implies. It does not explicitly state read-only semantics or return format, but 'List' strongly implies a non-mutating read.

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 short paragraphs, front-loaded with the core purpose, followed by a single packed sentence covering auth prerequisite and remediation. Every sentence earns its place and there is no filler or repetition of schema content.

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 listing tool with no output schema, the description covers purpose, authentication prerequisite, and the retry workflow. The only gap is the unspecified result shape, which the absent output schema leaves to the agent, but this is minor for such a simple tool.

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 takes zero parameters, so the baseline is 4. The description adds that the results are scoped to 'the authenticated account,' which defines the effective query context in place of any filter parameters.

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 ('List all phone numbers') plus the scope ('associated with the authenticated account'). This clearly distinguishes it from sibling list_* tools, which target different entities like emails, assets, or domains.

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 note provides clear context: the tool requires a Proof account and prior authentication, and it names the exact remediation path ('sign in with start_login') before retrying. It does not explicitly contrast with alternatives such as list_emails or get_add_phone_status, but the precondition guidance is actionable and situation-specific.

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