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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so "Free, read-only" is redundant. What does add value is the disclosure of the payload — remaining credits, quotas and recent calls — which is otherwise absent because there is no output schema.

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 trigger and followed by the return contents. The only wasted clause is "Free, read-only," which restates the annotations rather than earning 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 read tool, the description supplies the trigger condition and the shape of the result, which is the information an agent would otherwise lack. Nothing material is omitted, though a pointer to the top-up sibling would round it out.

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 per the baseline there is nothing for the description to disambiguate. No parameter-level information is missing or misleading.

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: it returns remaining credits, quotas and recent calls. That is enough for an agent to know exactly what it gets back. It does not, however, distinguish itself from the obvious sibling recharger_credits (top-up), which it never names.

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?

"Use this when the user asks how many estimates or credits remain, or what limits apply" gives explicit trigger conditions rather than leaving usage implied. It stops short of naming the alternative to reach for instead (recharger_credits) or stating any exclusion, so it is clear context without routing.

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