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

readOnlyHint=true already signals a safe read operation. The description adds that results are unpaid/part-paid, oldest first, and filtered by customer name. It does not describe returned fields, but with annotations covering safety, this is acceptable.

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 a single, front-loaded sentence with no filler. Every phrase adds value: unpaid/part-paid, one customer, oldest first, search by name.

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 one-parameter, read-only tool with no output schema, the description sufficiently covers scope, ordering, and search key. It does not enumerate return fields, which might be useful but is not critical 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 has zero description coverage for the single 'customer' parameter. The description compensates by explaining it is a customer name, which is essential for correct invocation and adds meaning beyond the raw schema type.

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 it returns unpaid/part-paid invoices for a single customer, ordered oldest first, searchable by customer name. This distinguishes it from aggregate tools like ar_aging or search_documents.

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 implies use when needing open invoices for one customer and specifies search by customer name. It does not explicitly name alternative tools or exclusion scenarios, but the scope is clearly constrained to a single customer, providing adequate context.

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