my_phone_numbers

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

With no annotations, the description carries the behavioral burden; it does disclose the authentication requirement, which is the most important trait here. It never states that the operation is read-only/non-mutating, nor what happens when the user has no phone numbers stored, leaving those traits to inference.

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 sentences, zero filler, with the resource stated first and the prerequisite second. Nothing is redundant or buried.

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?

Low-complexity, zero-parameter tool with an output schema that documents the return shape, so the description need not explain return values. The auth caveat is the only real risk factor and it is covered; the read-only nature is the only minor omission.

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 there is nothing for the description to explain beyond what the empty schema already conveys. Baseline 4 applies.

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 phrase 'Phone numbers on your profile' names the specific resource and implicitly the retrieval operation, and it is distinguishable from siblings like my_addresses, my_profile and my_orders by resource scope. It stops short of an explicit verb such as 'list' or 'get', so the agent must infer that this is a read.

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?

'Requires login' states the prerequisite for calling it, which is genuine usage guidance. There is no explicit when-to-use versus alternatives (e.g. my_profile, which may also surface contact data) and no statement of when it returns nothing.

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