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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false. The description's "Does NOT change the balance" largely restates readOnlyHint in prose, but "Does NOT show other accounts" adds a genuine scope constraint not present in annotations. Useful but not rich additional behavior.

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?

Three short sentences, front-loaded with what is returned before the negatives. Slightly padded by the read-only restatement that annotations already cover, but nothing is bloated.

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, read-only account query with no output schema, the description adequately conveys the return content (balance plus recent spend) and the account scoping. Return shape details (format, time window of "recent") remain unspecified but are minor at this complexity.

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; the baseline for a no-parameter tool applies. No parameter guidance is 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 the resource (credit balance) and the extra payload (recent spend) in a specific way, so an agent knows immediately what comes back. It does not, however, differentiate itself from money-adjacent siblings such as estimate_cost, so the routing value is partial.

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 two negative statements scope what the tool will not do, but there is no statement of when to call it versus alternatives (e.g. estimate_cost for projections). Usage must be inferred from the purpose line.

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