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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful behavior (ascending sort by age, computed days-outstanding field), but leaves pagination/truncation behavior unaddressed despite a limit parameter, and doesn't say what state counts as 'marked as paid'.

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?

One sentence, front-loaded with the resource and filter criteria, then ordering, then the optional filter. No filler, no restatement of the title.

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 list with no output schema, the description covers scope, sort order, and a returned field, and annotations cover safety. It falls short only on result-volume/pagination behavior and the semantics of the customer filter, which are minor but real gaps.

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%, so the description must carry parameter meaning, and it largely does not. 'Optional customer filter' merely restates the parameter name without saying whether it matches customer ID, exact name, or a prefix, and the limit parameter (default 20, max 100) is never mentioned in the description.

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?

States a specific verb and resource ('List issued invoices not yet marked as paid') plus ordering ('oldest first') and an output field ('days outstanding'), which is far more precise than the sibling names (create_invoice_draft, sales_report, search_customers). An agent can distinguish this from the report and customer-search tools without opening any schema.

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 scope ('not yet marked as paid') implies the collection scenario, so when-to-use is inferable. However, it never says when to prefer sales_report or search_customers instead, and gives no prerequisites or exclusions (e.g., whether draft invoices are included).

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