get_usage_details

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

With no annotations provided, the description carries the full burden of behavioral disclosure, but it only states the action without explaining side effects, authentication requirements, or whether results are cached or live. The presence of password and username parameters hints at auth needs, but the description itself does not disclose this or any other behavioral trait.

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 a single, front-loaded sentence with no wasted words. It immediately states what the tool does and scopes it to the current billing period, making it easy to parse quickly.

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?

The tool has no output schema and no annotations, so the description needs to explain the return format and any operational context. It does neither, leaving the agent uncertain about what 'detailed usage breakdown' contains, whether credentials are actually required, and how this relates to the account overview sibling. For a tool with optional auth parameters, this is a notable gap.

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 100%, so the schema already documents all three parameters. The description adds no extra parameter-level detail, such as format requirements or interactions between the optional credentials and the line parameter. Baseline 3 applies because the schema handles parameter documentation adequately.

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 identifies a specific verb ('Get') and resource (T-Mobile data/call/text usage breakdown for the current billing period), so an agent can understand the tool's core function. It does not explicitly contrast with sibling tools like get_account_overview or pay_bill, but the resource is distinct enough that the purpose is unambiguous.

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 no guidance on when to use this tool versus alternatives such as get_account_overview. There is no mention of prerequisites, fallback options, or conditions that would make this the right choice. The usage context must be inferred entirely from the tool name and description.

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