Get an invoice

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely useful behavioral context beyond that: line-item titles and invoice notes are the practice's own free text and are subject to redaction unless include_contact_details is set. It does not disclose not-found/error behavior, but it meaningfully extends the annotation profile.

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 waste. The core capability (one invoice by id with line items) is front-loaded, and the redaction caveat follows immediately. Nothing is repeated from the schema or annotations verbatim.

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?

No output schema exists, so the description appropriately states what is returned (the invoice plus its line items) and explains the redaction behavior that affects the response. For a read-only, 2-parameter tool this is nearly complete; only not-found/error behavior is unaddressed.

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 50%: invoice_id carries only a UUID pattern while include_contact_details has a rich schema description. The prose compensates by explaining that free-text fields (line-item titles, notes) are the redaction target, which clarifies the practical effect of include_contact_details beyond the schema's own wording.

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+resource+scope: 'One invoice by id with its line items', which clearly distinguishes a single-record fetch from the sibling list_invoices. It falls short of 5 only because it never names the sibling explicitly and 'get/one' is left implicit rather than stated as a verb.

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?

Usage is implied by 'by id' — you fetch a specific invoice when you already have its id — but there is no explicit when-to-use guidance and no exclusion or alternative named (e.g., use list_invoices to find an id first). Adequate but leaves routing to inference.

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