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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered; the description nonetheless adds the non-obvious cost fact "no charge," which annotations do not express and which matters to an agent budgeting calls. It does not describe latency, caching, or what the balance represents.

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?

Two short sentences, front-loaded with the purpose and followed by the one behavioral fact that matters. Every clause earns its place; nothing is padded or redundant.

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?

With no output schema, the description is the only place return-shape information could live, and it says nothing about what a balance looks like (units, currency, whether it is a number or an object). For a simple read tool with full annotation coverage this is a minor but real gap.

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 takes zero parameters and the schema is a strict empty contract, so there is nothing for the description to clarify. Baseline 4 applies; no parameter-level semantics are needed or missing.

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?

States a specific verb and resource ("Get your credit balance"), which is instantly distinguishable from every sibling, all of which concern export jobs/tools. It stops short of a 5 only because it never explicitly contrasts itself with alternatives — it relies on the resource name alone to do that work.

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?

Usage is only implied: an agent reads this as "call when you need to know the current balance." There is no explicit when-to-use statement, no prerequisites, and no mention of alternatives (none exist among siblings, but that is left to inference). Adequate for a trivial zero-arg getter, not strong guidance.

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