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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, so the safety profile is covered. The description adds a useful, explicit reassurance that the call cannot touch billing, which is meaningful context beyond the annotations for a tool that exposes financial data, though it omits auth requirements or any rate-limiting behaviour.

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?

Two short sentences with zero filler, and the core purpose is front-loaded before the clarifying constraint. Nothing repeats the tool name or title.

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 parameterless read tool with no output schema, the description names the three data categories returned (credits, quota, usage history) and rules out side effects, which is nearly everything needed. It stops short of indicating the format or time granularity of 'usage history', a minor gap given there is no output schema to fall back on.

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 no parameters (schema has an empty properties object), so there is nothing for the description to disambiguate; the baseline for a zero-parameter tool applies.

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 specific verb (Get) and specific resources (credits, quota, usage history) scoped to the organisation. No sibling tool touches billing or usage data, so an agent can immediately tell this is the only relevant choice.

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 rather than stated — there is no explicit 'use this when...' or exclusion of alternatives. However, with zero parameters and no competing sibling, the practical ambiguity is low, and the 'Does not modify billing' line does head off a misread of intent.

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