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

Beyond the annotations (which only declare readOnly=false, destructive=false, idempotent=false), the description adds real operational context: the 24-hour download URL lifetime, computed totals in the response, and the anonymous rate limit with the api_key/Authorization escape hatch. It stops short of saying each call consumes quota or whether generated documents persist server-side.

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 action and immediately followed by the return value and the auth/quota caveat. 'Professional' is mild filler, but nothing else is wasted.

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 output schema, the description supplies the essential return contract (download URL, 24h validity, computed totals) plus auth and rate-limit behavior, which is what an agent needs before calling. Gaps remain around document persistence and the format option, but the core is covered for a nested-schema create tool.

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 33%, so the description should carry more weight; it does summarize the data payload as parties/line items/tax/discount and explains the api_key quota behavior, but says nothing about the options.format parameter (A4 vs LETTER) or the nested optional party fields. Useful orientation, incomplete compensation.

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?

Clear specific verb+resource: 'Generate a professional invoice PDF from structured JSON', with the input shape (parties, line items, tax, discount) sketched in. It implicitly separates itself from create_receipt_pdf and create_einvoice_xml by naming the invoice PDF output, though it never names those siblings explicitly.

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 description gives quota/auth context (10 documents/day anonymous, api_key for plan quotas) but never says when to choose this over create_einvoice_xml or create_receipt_pdf, or what conditions favor one output format over another. Usage is implied rather than guided.

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