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

Annotations already establish readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful context beyond that: it states the call takes no parameters and is 'cost: free', which tells the agent it can call it liberally without consuming credits.

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?

A single compact line: category tag, purpose, returned fields, invocation note, and cost. Nothing is redundant and the key information is front-loaded.

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 tool with no output schema, the description does the necessary work by naming the contents of the result. Rate limits or refresh cadence would be nice but are not essential for correct invocation.

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 parameters, so the baseline is 4. The description reinforces this with '无需参数', leaving no ambiguity about how to invoke 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?

Specific verb plus resource: it queries the caller's platform usage summary and enumerates the three fields returned (today's bars, this month's tokens, remaining quota). That separates it reasonably from platform_user_subscription and platform_account_overview, though the distinction from the latter (usage vs. account overview) is left implicit.

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?

Usage is implied by the content ('my usage summary'), so an agent can infer this is the tool for checking quota consumption. However, there is no explicit when-to-use versus the nearby account/subscription tools, and no when-not-to-use or prerequisites.

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