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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description contributes only the REST endpoint path (GET /invoices), which adds no operational context such as pagination semantics, result ordering, or default limit behavior — all of which matter for a list endpoint.

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 short sentences, front-loaded with the purpose; nothing is bloated. The trailing 'Orb API: GET /invoices' is largely decorative and could be dropped, keeping a clean 4.

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 tool, the definition is minimally adequate. There is no output schema, and while pagination is documented via the cursor/limit parameters, the description never explains paging flow or default page size, leaving a modest gap.

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 each of the 8 parameters (limit, cursor, status, due_date, date_type, customer_id, etc.) is already well documented in the schema. The description's mention of filters adds nothing beyond what the schema provides, so the 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 and resource ('List invoices') plus the optional filter dimensions (customer, subscription, status). It is clearly distinguishable from the singular orb_get_invoice by verb, but it never explicitly contrasts itself with that sibling or explains list-vs-get behavior.

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 phrase 'optionally filtered by customer, subscription, or status' implies when this tool is useful (browsing/filtering a collection), but there is no statement of when NOT to use it or which sibling (e.g. orb_get_invoice for a single invoice) to prefer.

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