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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'Read'. It adds useful context beyond annotations: the data is private, and the required key type is a utility key rather than a health owner key. This is meaningful auth/scope information not captured by the annotations.

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, both essential, with the primary purpose front-loaded. There is no filler or redundant restating of the tool name.

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?

Given the simple single-parameter schema, the output schema, and annotations covering safety, this description is complete. An agent knows the operation, the auth requirement, and the data scope. Nothing critical is missing for selecting and calling the tool.

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?

Schema documentation coverage is 0%, so the description must compensate for the api_key parameter. It partially does by explaining that the tool requires a 'utility key', which tells the agent what kind of value api_key expects. It could be more explicit about how to obtain or format the key, but the key type is meaningful.

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 uses a specific verb ('Read') with a clear resource ('private coin balance and usage ledger'), and the sibling create_utility_account makes the read-vs-create distinction obvious. An agent can tell exactly what this tool does and what it does not do.

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 gives a clear usage context: reading account data, and it states a prerequisite/auth requirement ('Requires a utility key, not a health owner key'). It does not explicitly name alternative tools or when to prefer them, but the context is strong enough that an agent would not reach for create_utility_account or the health-related siblings.

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