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

With no annotations provided, the description carries the full burden of behavioral disclosure. It details return fields (tokens used, remaining, monthly allowance, billing plan, reset time) and explicitly states the cost is 0 tokens. This goes beyond a simple read operation and gives the agent clear expectations.

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 three terse, front-loaded sentences. The first sentence states the core action, the second lists key return values, and the third provides actionable usage guidance and cost. Every sentence earns its place with no 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 simple zero-parameter tool, this description is fully complete. It covers what the tool does, what it returns, when to use it, and the associated cost. The output schema is not shown but the description sufficiently documents the return fields, making the tool's behavior fully understood.

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 input schema has zero parameters, so there are no parameter semantics to explain. Per the baseline for zero-parameter tools, a score of 4 is appropriate. The description adds meaning by specifying the payload of returned data, even though it doesn't clarify parameter usage since none exist.

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 'Get the current API token balance for the authenticated account.' This is a specific verb+resource combination that precisely defines the tool's function. It distinguishes itself from all sibling tools, none of which relate to token balance.

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 explicit usage guidance: 'Use this before expensive calls or when you receive a 402 insufficient_tokens response.' It also notes that the tool costs 0 tokens, which is critical for cost-aware decision-making. No sibling tool serves the same purpose, so no alternatives are needed.

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