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

Beyond the readOnly/non-destructive annotations it states there are no side effects ('creates no order and charges nothing'), the cost profile ('Free'), and the auth scope ('Any key can use it'), plus a known failure mode. It also names the two returned fields, which matters since no output schema exists.

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?

Five short sentences, front-loaded with what is returned and followed by when to call it and what it costs. Every sentence carries either a return detail, a trigger, or a constraint.

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 is the only place to learn the return fields and failure modes, and it covers both. An agent has everything needed to call it and interpret the response correctly.

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 there is no argument semantics to explain and the description does not need to compensate for anything. It spends the space on return values instead, which is the only useful detail available.

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?

It gives a precise verb plus resource and even names the exact values returned ('url', 'balance_usd'), so there is no ambiguity about what the tool does. It implicitly separates itself from purchasing tools by stating it creates no order, though it never names a specific sibling such as everyinfra_create_ticket for billing escalation.

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?

It lists concrete trigger conditions (a call failing with quota_exhausted or ai_topup_required, or the user asking how to add funds) and a negative case (accounts whose service provider handles top-ups return topup_unavailable). This is explicit when-to-use guidance, not inference.

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