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

readOnlyHint=true already establishes this as a safe read, so the bar is lowered. The description still adds genuinely useful behavioral context beyond the annotations and schema: the unit convention ('Amounts are in cents') and the underlying endpoint (GET /invoices). It stops short of describing pagination defaults or result ordering, which keeps it from 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 compact sentences plus a short endpoint tag. The core purpose and scope lead, the filter axes and example follow, and the unit caveat is placed last where it belongs. No filler.

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 read-only list tool with full schema coverage and no output schema, the description covers scope, filter axes, units, and the API mapping. It does not describe the shape of a returned invoice record or default paging behavior, a minor gap given the tool's straightforward list semantics.

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 13 parameters including enums and ISO-8601 formats are already documented in the schema. The description restates the filter categories at a higher level and adds one combined-filter example, but contributes no syntax or constraint detail the schema lacks. 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 a scope qualifier ('across the company') and enumerates the filter axes. The company-wide scope implicitly distinguishes it from housecall_list_job_invoices, but it never names that sibling, so the differentiation is inferential rather than explicit.

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?

Gives a concrete usage example ('everything open and overdue') and lists the available filter dimensions, which implies when the tool is useful. However it offers no when-not guidance and never mentions housecall_list_job_invoices as the narrower alternative, leaving the agent to infer selection.

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