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

Annotations already establish readOnly, idempotent, non-destructive, and openWorld behavior, so the description is not carrying the full safety burden. It adds useful behavioral context by stating the call is 'Free' and 'changes nothing,' and it discloses the information returned, though it does not discuss auth, rate limits, or response shape.

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 dense but purposeful sentences. The primary content is front-loaded in the first sentence, and the second sentence adds only actionable usage guidance and a cost/side-effect note, with no wasted prose.

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 must explain what the call returns and when to use it. It does both in detail, covering account balance fields, spend cap fields, pause state, auto-recharge, and token expiry, which is enough for an agent to call it 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 has zero parameters, so the baseline is 4. There is no parameter meaning to explain, and the description correctly does not fabricate any input semantics.

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 uses a specific verb-resource pairing and enumerates exactly what the balance and spend-cap result contains: payable balance, running machine cost, runway, pause status, auto-recharge, cap limit, committed amount, remaining amount, longest rental, and token expiry. This clearly distinguishes it from every sibling tool, which are deployment, rental, listing, event, and market tools.

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 gives explicit usage context: 'Call it before long jobs and whenever an alert mentions the balance.' It does not name alternatives or when-not conditions, but there is no sibling tool that overlaps with balance/spend-cap checking, so the guidance is clear without needing exclusions.

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