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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds a genuinely non-obvious trait: 'Free: does not use a request,' which tells the agent this call is quota-neutral and safe to repeat. It also points to an upgrade URL for the 'need more' case. It stops short of describing the exact response shape, but that is a modest gap.

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?

Front-loaded with the primary outcome, then the quota-cost note, then the trigger condition, then the upgrade link – every sentence is short and earns its place. The trailing marketing URL is slightly tangential but contextually relevant after a limit error.

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?

With no input parameters and no output schema, the description bears the burden of explaining the return payload, and it does so by enumerating all four returned values. An agent has everything needed to call it and to interpret the result.

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 disambiguate; baseline 4 applies. The absence of any parameter discussion is correct rather than an omission.

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 ('Shows') and enumerates exactly what is returned: plan, requests used this month, requests left, and reset time. This clearly distinguishes it from the sibling data-retrieval tools (top posts, trends, time series), which return analytics rather than account state.

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 invocation triggers: the user asking about their limit, or a limit error having occurred. That is actionable guidance beyond mere implied usage. It does not state when not to call it or name an alternative, but no sibling covers this ground, so the omission is minor.

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