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

Annotations already indicate readOnlyHint=true, so the description adds value by explaining the output is bucketed by age and spans all customers. It does not mention return format, but that is not required given the read-only nature and no output schema. No contradiction with 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?

The description is two sentences, front-loaded with a clear question and purpose, and includes a direct pointer to an alternative. Every sentence 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?

For a simple read-only report with one optional parameter and no output schema, the description covers the core purpose and when to use it. However, it omits explaining asOf, which is a minor completeness gap. Overall, it is sufficient for tool selection.

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 0%: the only parameter 'asOf' is not explained in the description. The description never mentions that an optional as-of date can be provided, leaving the agent to infer its meaning from the name and pattern. This is a notable gap.

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 the tool generates an accounts-receivable aging report across ALL customers, bucketed by age. It uses a specific verb and resource ('accounts-receivable aging') and distinguishes itself from the sibling tool open_invoices, which targets a single customer.

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?

It explicitly provides an alternative: 'For the unpaid invoices of ONE named customer, use open_invoices,' guiding when to use this tool vs. another. It also implies the scope is all customers, making the usage context clear.

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