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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorld, so safety is covered. The description adds value beyond them by labeling the call 'Free' (calling it costs no credits) and by framing the tool as the recovery path when another tool reports insufficient credits, which is real behavioral context the annotations cannot express.

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 return contents are front-loaded in the first sentence, with usage guidance following in priority order and 'Free' isolated for emphasis. It runs a bit long in prose and the clause 'instead of just reporting a failure' is slightly redundant, but every sentence still carries actionable information.

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?

There is no output schema, so the description must carry the return shape itself, and it does by naming the three components: balance, monthly grant, per-action costs. It omits units, field naming, and whether refill timing is a returned value or inferred, which keeps it just short of fully self-contained for a schema-less response.

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, so there is nothing for the description to disambiguate and the baseline is 4. Nothing in the text misleads about inputs.

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 names exactly what is returned: the account's current credit balance, its monthly grant, and the cost of priced actions. That is a specific resource plus returned fields, and it is unmistakably distinct from every sibling tool, all of which deal with creators, lists, or campaigns.

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?

It gives two explicit triggers: check before proposing anything expensive so you can quote the real impact of a crawl or live post fetch, and check when a tool reports the account is out of credits so you can say when the balance refills. Both the when and the purpose of each call are stated, with no exclusions left implicit.

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