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

No annotations are provided, so the description carries the full burden, and it does much of that work: it declares the read nature ('CompanyMember read'), the status lifecycle draft→issued→cancelled, that document_no is null on a draft, and that payment_status/open_amount are derived from the linked open item. It omits what happens on a nonexistent or cross-company invoice_id (error vs empty), which a mutation-free read tool could still usefully state.

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?

Front-loaded with the resource and its arm, then the payload, then the routing caveat. It is longer than typical, but with no output schema the field enumeration (net/vat/gross, document numbers, snapshot ids) is load-bearing rather than padding; only the parenthetical field lists feel slightly over-stuffed.

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?

With no annotations and no output schema, the description is the only place an agent can learn the return shape, and it covers header, line amounts, totals, lifecycle states, document linkage and derived payment fields, plus scope exclusions. Nothing an agent needs to call it correctly is missing.

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?

Two required parameters with 0% schema description coverage, so the schema adds nothing. company_id and invoice_id are largely self-evident from their names and the 'CompanyMember read' hint, but the description never explains the tenancy/scoping relationship between them or the accepted id format. Adequate, not additive.

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 resource and scope: a single authored outgoing AR invoice with its lines, plus the exact payload it carries (header, lines with computed amounts, totals, lifecycle). It explicitly distinguishes itself from the ingested 'item' arm and from list_ar_invoices / get_item siblings, so an agent can pick it without opening a schema.

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 clear when-not rule ('a receivable that arrived as an ingested document is an item, not an ar_invoice') and routes follow-up needs (journal entry, settling bank transactions, credit-note chain) to the related endpoint. It does not mention how to obtain the invoice_id (e.g. via list_ar_invoices), so the routing story is strong but not fully closed.

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