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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true). The description adds real value beyond that by disclosing the fields present in each returned record — important because there is no output schema — plus the status vocabulary (draft, sent, past_due, etc.) that the schema does not enumerate. It omits pagination behavior and rate limits, keeping it below a 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?

Two sentences, front-loaded with the resource and its returned shape, followed by filtering and the endpoint. The status enumeration is long but carries information absent from the schema, so it earns its space.

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 10-parameter, zero-required list tool with nested objects and no output schema, the description supplies the return-field inventory and filtering overview that structured fields cannot. Pagination mechanics live in the schema, so the only genuine gap is the absence of output-shape/pagination prose.

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 10 parameters (including the nested filter and metadata objects) are already documented in the schema. The description reinforces the filter categories at a high level but adds no format or syntax detail 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?

Specific verb+resource (list invoices) with an explicit enumeration of returned fields (number, customer, status, dates, totals, balance, line items) and the endpoint GET /invoices. It does not name the sibling it should be chosen over (e.g. invoiced_get_invoice for a single record), so it stops short of full sibling differentiation.

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 filter clause ("Filter by customer, paid flag, invoice date range, update time or any exact-match column") implies when the tool is appropriate, but there is no explicit when-to-use vs. when-not guidance and no reference to the single-invoice or other list siblings.

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