Get account balance

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

The readOnlyHint annotation confirms this is a safe read operation. The description adds behavioral context beyond the annotation by noting that running agents spends the balance, making the account state relevant to subsequent actions. It does not contradict the annotations.

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?

The description is only three sentences, all of which carry useful information: purpose, usage context, and an explicit alternative plus output format clarification. It is front-loaded and free of filler.

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 zero-parameter, read-only balance tool, the description is complete: it states what is returned, when to invoke it, and how it relates to other tools. No significant information gaps remain.

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?

There are zero parameters, so the schema imposes no burden and the baseline is 4. The description adds extra meaning by explaining the balance_usd output format, which is useful, though not strictly parameter-related.

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 clearly identifies the tool's purpose: retrieving the authenticated account's US-dollar balance and plan. It uses a specific verb and resource, and distinguishes itself from get_usage by explicitly noting that get_usage is for where money went.

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?

The description provides clear usage guidance, stating that agents spend this prepaid balance and that users should check it before invoking agents. It also explicitly directs users to get_usage for expense details, offering a concrete alternative.

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