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

Annotations already mark this as read-only and non-destructive. The description adds valuable behavioral context beyond that: it specifies the data source ('all paid, non-sample invoices'), the aggregation ('aggregate customer totals'), and the output shape ('without invoice rows'). This goes beyond the annotations without contradicting them.

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 sentences with no fluff. The primary action and scope are front-loaded, and the additional details (invoice filtering, output format) are concise and relevant. Every word earns its place.

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 output schema, the description partially explains the return: 'returns aggregate customer totals without invoice rows'. This gives a high-level understanding, though it omits specifics like ordering or exact fields in each result. For a simple read-only report with well-documented parameters, this is sufficient but not exhaustive, so a 4 is warranted.

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 input schema covers 100% of parameters with meaningful descriptions (period, from, to, limit). The tool description does not add any extra context about parameters, but since the schema is comprehensive, the baseline of 3 is appropriate.

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 states a specific verb ('ranks'), a specific resource ('named customers'), and the basis ('paid invoice revenue'), along with the workspace scope and the filtering of sample invoices. It clearly distinguishes this report tool from any general search or other report sibling by its singular focus on customer revenue ranking.

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 clear context for when this tool is useful (when you need a customer revenue ranking), but it does not explicitly mention alternatives or when not to use it. There are sibling report tools like reports-by-location and reports-overview, but no cross-referencing; the implied usage is still apparent.

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