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

Goes well past the annotations: it discloses unit consumption for live/signed-in agents vs free watermarked test keys, that only the published template version renders (null published_version -> template_not_found), that failures return status failed with code and message, that the download link expires at expires_at, and that image renders under 2 MB inline the picture. 'Every call is a new render' is consistent with idempotentHint=false rather than a restatement.

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 and nearly every sentence carries distinct information (outputs, alternatives, billing, failures, e-invoice, link expiry). It is a single dense block, though, with several parenthetical asides packed together, which costs some scannability.

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 nine-parameter, nested-object, mutation-style tool with an output schema and annotations, the description covers outputs, defaults, billing, failure modes, pre-validation steps, e-invoice behavior and link lifetime. An agent has everything needed to invoke it correctly and interpret the result.

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% and the schema already describes data, html, wait, engine, locale, output, einvoice, filename and template thoroughly, including the enum semantics. The description reinforces the template-versus-html choice and the einvoice/data._invoice coupling but adds little parameter-level detail the schema doesn't already carry, so the 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?

Opens with a specific verb and resource — creates a document by filling a stored template or ad-hoc html — and immediately enumerates the concrete outputs (PDF, image, DOCX/PPTX from Word/PowerPoint templates). It actively differentiates itself from named siblings: convert_to_pdf for office conversions, validate_template for pre-checks, check_invoice for e-invoice validation, get_render for fresh links.

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?

Explicit routing: 'Use it to make a document from data; to turn an existing office file into a PDF, use convert_to_pdf,' plus 'validate_template finds most causes beforehand' and 'check the block with check_invoice first.' The conditions that select each alternative are stated, leaving nothing to inference.

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