usage

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

With no annotations, the description carries the full burden and does reasonably well: it discloses the rolling-24h window, that it is scoped to the calling key, and the three counters returned. It is implicitly read-only ('Show') and safe, but it never says whether the numbers are eventually consistent or how the limit is enforced.

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, no filler: the first states what is returned and over what window, the second states when to call it. The most decision-relevant content is front-loaded and every clause earns its place.

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 output schema, the description must describe the return payload, and it does by naming the three counters. Combined with explicit invocation triggers and the rolling-24h window, an agent has everything needed to call it correctly and 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; the baseline for a no-parameter tool is 4. The description correctly implies that scope comes from the calling API key rather than from arguments.

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 gives a specific verb and resource: it shows 'this API key's rolling-24h usage against its limits' and enumerates the returned metrics (calls made, calls allowed, contact lookups used). That is far more concrete than the bare name 'usage', though it never explicitly contrasts itself with siblings like batch_enrich, which it implicitly serves.

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?

It gives two concrete trigger conditions: call it 'when you hit a rate-limit error or before a large batch.' This tells the agent exactly when to reach for it, and no sibling tool offers this capability, so no alternatives need naming. No exclusions are stated, but none are meaningful for a no-argument status read.

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