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

Annotations already disclose the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), so the description's added value is cost and lifecycle: 'Each requested format costs 1 render credit' and returns hosted URLs with expiry. That is real, decision-relevant context an agent needs before choosing both formats. It does not explicitly warn that the operation is non-idempotent and re-invocations consume additional credits, which keeps it from a 5.

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?

Four sentences, front-loaded with the trigger condition followed by the capability, branding knobs, return shape, and cost. Almost no filler. Minor redundancy in listing both the document types and the Markdown/HTML phrasing, but it is efficient overall.

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?

There is no output schema, yet the description supplies the return shape ({ pdfUrl, pngUrl, shareUrl, expiresAt }), and the cost model, which is exactly what an agent needs to decide whether to call and what to expect back. With 11 parameters all documented in the schema and a nested pageSetup object fully described there, nothing material 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?

Schema coverage is 100%, so every parameter is already documented in the schema, and the description largely restates the prominent ones (logo, accentColor, font, header, footer, format choice). The one added nuance — that formats are billed per render credit — is already in the formats schema description. Baseline 3 is appropriate where the schema does the heavy lifting.

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 concrete transformation: Markdown or HTML becomes a branded, downloadable artifact (PDF, PNG, hosted share page). It names the resource types users ask for (report, invoice, summary, release notes) and the branding controls, so an agent can distinguish it from siblings like rendex_screenshot or rendex_render_link 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?

Strong trigger guidance: 'Use this when the user asks to make or create a branded report, invoice, summary, release notes, or document — or to turn this Markdown/HTML into a PDF and PNG.' It gives concrete user phrasings rather than an inference. It stops short of explicit exclusions or naming when to prefer a sibling such as rendex_screenshot, so it falls one step below the top score.

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