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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds value by disclosing that the response includes expiry timing and auto-reload state, but says nothing about permission requirements, what happens with no org, or freshness/caching of the balance.

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?

One short line with no filler, and the most useful information (what data comes back) is front-loaded. It reads as a fragment rather than a sentence, which slightly weakens framing but costs nothing in length.

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?

This is a simple read-only single-parameter tool, but there is no output schema, so the description carries the burden of explaining return values. It lists the three top-level items but gives no shape, units, currency, or time format for the expiry and balance.

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?

Schema coverage is 100% and the single `org` parameter is documented there, including its default. The description adds no meaning about the org parameter or how balances differ per org, so baseline 3 is appropriate.

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 names the specific resource and enumerates the three pieces of data returned (credit balance, next expiry, auto-reload), which lets an agent distinguish it from cloud_billing_ledger and cloud_billing_code. It is a noun phrase with no explicit verb, but the read intent is unambiguous.

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?

No guidance on when to call this versus cloud_billing_ledger or cloud_billing_code, and no note that it scopes to a single org. The agent must infer usage purely from the name and the return-fields list.

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