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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety and repeatability are covered structurally. The description adds that the value is 'current' (i.e. a live figure) and denominated in SGD, which is useful context beyond the annotations. It does not disclose freshness/latency or what happens when a meter has no prepaid account.

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?

A single short sentence with the key qualifiers ('current', 'prepaid', 'SGD') front-loaded and no wasted wording. It is arguably terse to the point of omitting routing guidance.

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 only two fully documented required parameters, an output schema covering return values, and annotations carrying the safety profile, the description is nearly complete. The one real gap is disambiguation from the three sibling meter/top-up tools.

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 description coverage is 100%, with both meter_id (8-digit pattern) and system (enum of institutions) fully documented in the schema. The description adds no meaning beyond that, so the baseline 3 applies.

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 ('Get'), a specific resource ('current prepaid credit balance of a meter') and adds the currency unit (SGD). An agent knows exactly what is retrieved, but the description does not distinguish this from siblings such as get_meter_usage or get_recent_topups.

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 implied by the name and by 'prepaid credit balance', so an agent can infer this is the balance-check call rather than a consumption or top-up call. However there is no explicit when-to-use guidance and no mention of the sibling tools or when to prefer them.

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