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

Richly exceeds the readOnly/idempotent annotations by explaining what counts toward quota (automation replies, manual replies, comment-to-DM, per-recipient broadcasts, per-contact sequence steps) versus what does not, plus the 20% margin and hard pause at 100%. Minor deduction only because the pause/consumption mechanics are described as fixed policy without noting any edge cases or timing of quota resets beyond 'billing date'.

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?

Front-loaded with the core resource and dense with useful detail, but the single long sentence with stacked parentheticals (plan tiers, add-on pricing) is harder to scan than it needs to be. Every fact broadly earns its place, though the exact dollar add-on figure is marginal.

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 and no parameters, the description fully specifies what is returned (quota consumption and per-account message counts) and the behavioral rules an agent needs to interpret the result, including when DMs pause.

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 tool takes zero parameters, so the schema carries no semantics to compensate for; baseline 4 applies. The description appropriately spends no space on nonexistent inputs.

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 precise verb and resource: retrieves the organization's DM quota for the current billing period plus messages sent per connected account. It explicitly carves out the sibling get_x_usage for X, so an agent can distinguish the two without inspecting schemas.

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 explicit triggers: check before a big broadcast or sequence (noting one that doesn't fit cannot launch), and when the human asks why messages stopped. It also names get_x_usage as the alternative for X DMs, leaving nothing to infer.

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