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

Annotations already declare the safe read profile (readOnlyHint, destructiveHint=false). Beyond that, the description adds real behavioral context: the default unpaid-first / oldest-due-date ordering, the implicit unpaid default filter, that amounts are in account currency, and that a Cotlet API key with app access is required. Return format and pagination are not covered, holding it below 5.

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 first two sentences are near-duplicates ('Invoices with client, amount, due date...' vs 'Lists invoices with client, amount, due date and status'), wasting an opening line. The sort/default/auth facts are useful and reasonably front-loaded, but the text could shed a full sentence.

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 correctly carries the burden of describing returned fields, sort order, defaults, currency, and auth. It is largely sufficient; only pagination behavior and a clearer when-to-use note are missing.

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 100%, so all four parameters (limit, since, status, client_id) are already documented in the schema. The description echoes the client/date filtering and undefined default currency but adds no syntax or format detail beyond the schema. Baseline 3 applies.

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+resource ('Lists invoices') and enumerates the returned fields (client, amount, due date, status, days past due). An agent can distinguish it from service-autopilot_create_invoice or send_invoice without opening a 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 description implies usage through its default ordering ('Unpaid invoices come first by default, oldest due date first') and filter hint ('Filter by client or date'), but never states when to reach for this tool versus get/create/send invoice or any sibling. Guidance is inferable, not explicit.

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