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

Annotations already establish readOnly, idempotent, non-open-world, so the safety profile is covered. The description adds genuinely useful context beyond that: the Trial-key quota of 100 requests/day and the diagnostic value after rate_limited/key_expired responses. It stops short of describing auth setup or whether quota resets on a rolling or fixed window, but the added behavioral context is substantial.

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 returned fields and then the actionable triggers. Every clause earns its place, including the parenthetical quota figure.

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 read tool with no output schema, the description fully compensates by enumerating the returned fields (plan, rate limits, expiry, today's request count) and by anchoring usage to two concrete scenarios. An agent has everything needed to call it correctly.

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 surface to document; the baseline for a 0-param tool is 4. Nothing in the description misrepresents inputs.

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+resource (get account usage) and enumerates exactly what is returned: plan, rate limits, expiry, and today's request count. This is clearly distinguishable from the odds/events siblings, which all deal with sports data rather than account metadata.

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 explicit when-to-use triggers: call it before a long analysis to check remaining quota, or after a call returned rate_limited or key_expired. Names the concrete error conditions that select this tool, leaving nothing to inference.

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