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

Annotations already declare readOnlyHint and destructiveHint false. The description adds useful context beyond annotations by explaining that 'held' is reserved by in-flight runs and by noting this endpoint also serves as a cheap key probe. No contradictions with 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 one efficient, front-loaded sentence followed by a docs link. Every phrase earns its place: the currency, the three balance components, the in-flight reservation clarification, and the key-probe behavior.

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 low-complexity, read-only tool with no output schema, the description covers the main return fields and purpose. The phrase 'cheapest probe that the key works' is slightly awkward and could be clearer, but it does not prevent an agent from understanding how to use the tool.

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, and schema description coverage is 100%, so the baseline for parameter semantics is 4. The description adds no parameter-specific details, but none are needed given the absence of parameters.

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 states the tool retrieves the workspace's balance in USD and explicitly names the returned components: balance, held, and available. It also adds a distinct secondary purpose (cheapest key-working probe), making it easy to distinguish from siblings like inspect or search.

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 intended use is clear: check the workspace balance and verify the API key works. It does not explicitly mention when not to use it or compare against sibling tools, but the context is self-evident enough for a simple read-only balance check.

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