x_usage_get

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

Beyond the readOnlyHint and destructiveHint annotations, the description adds crucial behavior: the numbers are READ COUNTS, not money; X publishes no spend API; the session estimate is local, advisory, and resets on server restart. This is exactly the kind of non-obvious behavioral context an agent needs to interpret results correctly.

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?

Three sentences, each earning its place: what the tool reports, the critical caveat about read counts vs money, and when to use it. The most important semantics are front-loaded, and there is no redundant 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?

The description is complete for a read-only usage tool: it explains the report scope, the important caveats about the data source, the reset behavior, and the intended use case. The presence of an output schema means return structure does not need to be restated, and the annotations cover the safety profile.

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 description coverage is 100%, so the schema already documents both parameters (raw and days) well. The description mentions an 'optional per-day and per-app breakdown' but does not directly map this to the parameter names or add new parameter-level detail. This meets the baseline but does not exceed it.

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 clearly states a specific verb ('report') and resource ('post-read consumption of the current billing cycle against the monthly project cap'), and defines the tool's scope well. It does not explicitly differentiate from the similar sibling x_rate_limit_status, but the focus on billing-cycle read counts and local credit estimates is distinctive enough.

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?

The description gives an explicit usage context: 'Use it to check headroom before a high-volume read.' This clearly signals when to call the tool. It does not name alternatives or state when not to use it, but the guidance is actionable and sufficient for most agents.

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