Check usage and limits

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so 'Read-only' merely restates structured data. What the description genuinely adds is scope: the snapshot is per-account and limited to today's usage against daily limits. It does not mention how or when daily counters reset, which would have been a useful behavioral detail beyond the annotations.

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 sentences, front-loaded with the resource and its contents, followed by the usage trigger and a closing safety note. Every clause carries information and nothing is padded.

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?

An output schema exists, so the description need not enumerate return fields, and it still previews the key values (usage today, limits, remaining). For a zero-parameter read-only tool this is nearly complete; the only unstated detail is the reset/timezone semantics of 'today,' a minor 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?

The tool takes zero parameters, so there is no parameter meaning to add; baseline 4 applies. The description correctly implies the scope is fixed to the caller's own account with no filtering options.

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?

States a specific verb (show) and resource (account plan and today's usage), then enumerates the exact contents: texts and sign-in codes sent today, daily limits, and remaining count. It is clearly distinguishable from siblings like send_sms and send_sign_in_code, which perform sends rather than report capacity.

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?

Gives two concrete triggers: 'when the user asks about limits' and 'before sending several texts,' the latter implicitly routing the agent to check capacity before invoking send_sms/send_sign_in_code. It stops short of explicit when-not-use or exclusion conditions, so it is strong but not exhaustive.

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