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

The description adds behavioral context beyond the readOnlyHint annotation by explaining how the absence or presence of date parameters changes the output, and by specifying the grouping dimensions. It does not describe return structure, but it provides meaningful behavioral detail.

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 concise, front-loaded sentences. The first states the purpose, the second explains parameter behavior and output breakdown. Every word earns its place with no 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?

Given the tool has no output schema and only two optional parameters, the description covers the essential behavior: what is returned and how date ranges affect it. It could specify whether the breakdown is separate or combined, but for a summary tool this is sufficiently complete.

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 coverage is 0% (no descriptions for 'from' and 'to'), so the description must compensate. It does so by explaining the effect of date ranges vs. no dates. It implicitly maps the parameters to the range, giving them semantic meaning beyond the schema's basic format.

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 states 'How much you have sold' and specifies it covers invoiced sales, distinguishing it from other financial reports. It also mentions the breakdown dimensions (month, customer, product), making its purpose specific and unambiguous.

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 clear guidance on usage: with no dates it shows today and this month, with a date range it shows the period's sales. It does not explicitly mention alternatives or when not to use, but the context is sufficient for selecting the tool.

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