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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that it 'Uses one request', which is useful cost context for budget-sensitive agents, and lists what data is returned, though it doesn't mention auth requirements or freshness of 'live quota'.

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?

One dense sentence front-loads the resource and metric list, followed by example questions and a cost note. Every clause carries information an agent needs; there is no filler.

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 fully enumerates the returned metrics, including errors by status code and rate-limit usage. The single optional parameter is covered by schema, and the 'one request' note rounds out the operational context.

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 coverage is 100%, and the 'days' parameter is already fully documented in the schema with its default and maximum. The description adds no additional meaning about the window parameter, so baseline 3 is appropriate.

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 and resource ('Your account's API usage') and enumerates the exact metrics returned: requests, success rate, response times, errors, endpoints, quotas, and limits. This clearly separates it from siblings like diagnose_request, which handles individual request troubleshooting.

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 concrete example questions it answers ('why am I getting 429s?', 'when will my quota run out?'), which tells the agent when to reach for it. It does not name alternatives or state exclusions, but the usage context is unambiguous.

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