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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the description's 'retrieves data without changing records' largely restates structured data. It does add one genuinely useful behavioral fact — no credits are spent — plus the shape of the returned data, but says nothing about response format, freshness, or error cases.

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 the core action, with no wasted clauses. The opening 'Get wallet balance.' is near-redundant with the sentence that follows it, a minor trim opportunity.

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 parameters, no output schema, and full annotation coverage of the safety profile, the description carries exactly the load it needs to: what is fetched, that it is free, and that it is non-mutating. Nothing an agent needs in order to call it is missing.

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 the baseline is 4 and there is nothing for the description to disambiguate. The mention of pending charges and auto-reload settings clarifies what the parameterless call yields, which is a small value-add.

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 wallet balance') and enriches it with the payload contents ('pending charges and auto-reload settings'), which tells the agent what data comes back. It does not explicitly distinguish itself from the related wallet siblings (get_mail_wallet_pricing, get_mail_wallet_transactions), so it falls short of a 5.

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 by the resource itself — an agent can infer this is the balance-check tool. There is no explicit when-to-use, no exclusion telling the agent to prefer get_mail_wallet_transactions for history or get_mail_wallet_pricing for rates, and no prerequisites mentioned.

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