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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds real behavioral context beyond that: which fields free-text search covers, the accepted filtermode values, and the sourced filter recipe. It omits pagination defaults and sort determinism notes, which live in the schema.

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?

Three sentences, front-loaded with the purpose before the search scope and the special-case filter recipe. The inline JSON payload is dense but necessary; no filler sentences are present.

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 an 8-parameter read-only list tool with no output schema and full schema coverage, the description covers purpose, search scope, filter mode, and a tricky filter use case. The returned record contents are only sketched, but with no output schema that is a minor gap rather than a blocking one.

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 coverage is 100%, so the baseline is 3, but the description adds a concrete composite-filter example (invoice_items_source_type_eq + invoice_items_source_id_eq) that the schema's generic examples do not cover, plus the filtermode enumeration. That is meaningful semantics beyond the structured fields.

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 credit notes') and even enumerates the returned fields (number, dates, status, totals), so the agent knows exactly what this yields. It never names the sibling get_invoice to draw the list-vs-single distinction, but 'List' versus 'Get' is unambiguous from the names.

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 concrete, actionable guidance for a non-obvious case: finding one opportunity's invoices, including the exact filters payload and filtermode to pass. It does not state when to prefer a sibling (e.g. get_invoice for a single record) or when not to use it, which keeps it short of a 5.

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