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

Annotations already set readOnlyHint=true and destructiveHint=false, and the description does not contradict them. It adds useful behavioral detail: the result is denominated in USD and a valid key must be presented as a Bearer token. It does not cover error responses or rate limits, but for a simple read-only balance check the added context is adequate.

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, with the core function front-loaded and the authentication requirement as a concise second clause. No filler or redundancy.

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 single-parameter read-only tool with an output schema, the description supplies the essential facts: what is checked, the currency, and the required authentication. Nothing an agent needs to invoke it correctly 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 only parameter, context, is fully described in the schema (100% coverage), so the description does not need to document it. The Bearer-token mention clarifies that the API key is not a separate parameter but an auth header. This matches the baseline of 3 for high schema coverage.

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 a specific resource ('remaining wallet balance'), a unit ('in USD'), and an authentication context ('AnyAPI key supplied as a Bearer token'). It clearly distinguishes get_balance from siblings like get_api or run_api, none of which concern wallet balances.

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 description establishes that the tool is for checking the balance tied to the current API key, which implies using it before or instead of making billable API calls. It does not name alternatives, but the context is unambiguous given the sibling list contains no other balance-related tool.

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