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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds valuable behavioral context beyond that by stating the operation is free and does not consume credits, which is critical for an agent deciding whether to call it. It could further mention output format or authentication, but with annotations covering the read-only safety profile, this is sufficient.

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 two sentences with no filler. The primary purpose is front-loaded in the first sentence, and the second sentence packs cost information and usage triggers efficiently. Every word earns its place.

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, no-output-schema utility, the description covers all necessary aspects: what the tool returns, that it is free, and when to invoke it. There is no missing operational detail an agent would need to use 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 accepts zero parameters, so the input schema fully documents the absence of arguments. Per the rubric, 0 params yields a baseline of 4. The description adds nothing about parameters because none exist, which 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 states a specific verb and resource: 'Get the remaining credit balance for the Nephia account.' It clearly differentiates from siblings by addressing account-level balance rather than operation estimates or data queries, and the 'Free — does not charge credits' note further distinguishes it from charged 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?

The description explicitly states when to use the tool: 'Use this before a charged call, or after an insufficient-credits error.' This provides clear context and a decision rule, and since no sibling provides the same balance-checking function, there are no alternatives to exclude.

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