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

Annotations already declare readOnlyHint=true, so the safety profile is carried by structured data. The description adds the 'Orb API: GET /invoices' reference, which is consistent with read-only behavior and mildly informative, but it does not disclose pagination behavior, response shape, or rate limits. This is acceptable given the read-only annotation and simple list semantics.

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 sentences, zero filler: the operation and its filtering capability come first, and the API endpoint reference is a useful secondary detail. Every word earns its place.

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 filtered-list tool with 8 fully documented optional parameters, a read-only annotation, and no output schema, the description is nearly sufficient. 'List invoices' implies a paginated collection as the return, and the cursor parameter references pagination_metadata. The only minor gap is that it doesn't state the default page size or confirm the list response shape, but the schema largely covers this.

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 every parameter is already documented in the input schema (limit/cursor for pagination, status/due_date/date_type for filtering, and the three id filters). The description's mention of 'customer, subscription, or status' mirrors schema properties without adding new meaning, 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') and enumerates the key optional filters (customer, subscription, status), so an agent can tell it apart from orb_get_invoice by resource and verb alone. It never names a sibling explicitly, so it stops just short of full differentiation, which is why it gets a 4 rather than a 5.

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' gives clear context on how to narrow the listing, and the schema documents each filter. However, there is no when-to-use guidance versus alternatives like orb_get_invoice or orb_get_upcoming_invoice, and no exclusions are stated — usage must be inferred rather than stated.

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