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

The annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false. The description adds substantive behavior beyond that: it specifies the exact quota fields returned, notes that reset_at is UTC, mentions that some accounts receive a free_facts block, and clarifies that this call does not count toward the 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?

The description is three sentences and is front-loaded with what the tool returns, followed by the optional free_facts detail and the self-exemption caveat. Every sentence contributes useful information.

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-only quota-check tool with no output schema, the description provides enough detail about what is returned, the reset time semantics, optional account-specific data, and the quota exemption. Nothing an agent needs in order to call it correctly is missing.

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?

There are zero input parameters, so parameter semantics are inherently minimal and the baseline is 4. The description usefully explains the return fields even though there is no output schema, but it does not need to clarify input parameters.

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 states a specific verb and resource — returning the caller's current daily usage — and enumerates the exact fields returned (calls used today, daily limit, remaining calls, reset_at, and optional free_facts). It is immediately distinguishable from all sibling tools, which are financial/document analysis tools rather than quota tools.

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 makes clear this is for checking current daily usage and that the call is self-exempt from quota consumption, which is useful usage context. It does not explicitly say when not to use it or name alternatives, but there are no comparable sibling tools for account quota.

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