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

The description goes well beyond the readOnlyHint and destructiveHint annotations by explaining nuanced behavioral details: that channelSlots raise the effective channel limit by one, that unused slots are auto-canceled before renewal, and that per-slot autoRenews indicates renewal vs lapse at expiresAt. This is rich, non-obvious context that an agent would not infer from annotations alone.

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 appropriately sized for the complexity of the return data. It front-loads the primary usage summary, then explains the channelSlots semantics, which are essential and non-obvious. Every sentence earns its place without redundancy.

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 present, the description carries the full burden of explaining return values. It does so thoroughly by listing all major returned data categories and detailing the channelSlots structure, renewal behavior, and limits impact. Nothing critical is missing for an agent to understand what this tool provides.

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 input schema has zero parameters, and the description correctly makes no attempt to document parameters. With no parameters to explain, this baseline is appropriate and complete.

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 the tool's function: 'Check current account usage' and enumerates the specific resources it returns (post counts, scheduled post counts, channel counts, media storage usage, channelSlots). This is a specific verb+resource definition with enough detail to distinguish it from other tools like view_quota.

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 explicitly provides a usage condition: 'Use this when the user asks about plan limits or current usage.' This gives clear context for when to invoke the tool, though it does not name alternative tools or describe when not to use it.

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