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

With no annotations, the description carries the full burden and does well: it discloses authentication methods (x-api-key or Bearer sb_live_...), behavior without a key (explains how to get one), privacy stance ('no key, no tracking'), and what data is returned. It implies read-only via 'read surface' and 'statement' but could be more explicit about not modifying anything; it does not mention error handling or rate limits, so not a 5.

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?

The description is concise and front-loaded: it starts with the main output ('Your meter-account statement, live'), then details the contents, followed by authentication requirements and fallback behavior. Each sentence adds essential information without 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 tool with no parameters and no output schema, the description is quite complete: it enumerates the return contents, explains authentication, and covers the no-key case. It lacks explicit return format (e.g., JSON vs text) or possible failure responses, but given the simplicity, it is sufficiently complete for an agent to select and invoke correctly.

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 has 0 parameters and the schema is empty (100% coverage by default). The description adds context about authentication headers (x-api-key, Bearer) which is not in the schema, aiding the agent in constructing the request. Since there are no parameters, the baseline is 4, and the description adds no unnecessary parameter info.

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 clearly identifies the tool as providing a meter-account statement with specific contents: month-to-date metered Reads, tariff, watched topics with billing status, acceptance evidence, and daily cap. It distinguishes from sibling get_* tools by focusing on account/billing-specific data, using the phrase 'your meter-account statement' which is distinct from other tools like get_entity or get_watch_feed.

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 provides context on when to use the tool: it requires an identified key, and without a key it explains how to get one. It also mentions that read surfaces remain available in free anonymous lanes, giving an alternative access path. However, it does not explicitly compare to sibling tools or state exclusions for specific scenarios, so it falls short of a 5.

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