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

The description discloses critical non-obvious behaviors: JavaScript is not executed, external fonts/images are allowed, each call costs 1 credit, and the result is a temporary download link valid for 15 minutes. These details go well beyond the sparse annotations and materially affect how an agent should invoke and handle the tool.

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?

Every sentence earns its place: capability, rendering constraints, use cases, mode selection, cost, and output lifetime. It stays compact despite the tool's 10-parameter surface and front-loads the core purpose.

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 and a complex 10-parameter tool, the description supplies the missing integration-level facts: what the call returns, how long the link lasts, the credit cost, and rendering caveats. Combined with the fully described schema, it gives an agent enough to invoke the tool correctly.

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 100%, so the baseline is 3, but the description adds cross-parameter guidance by explaining the html-or-template+data decision and linking to the template catalog. It avoids repeating field-level details, which the schema already covers well.

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?

The title and opening line state exactly what the tool does: render HTML into an image in PNG, JPEG, or WebP. It distinguishes itself from siblings like html_to_pdf and screenshot_url by emphasizing HTML input, inline CSS, no JavaScript execution, and image output.

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?

It gives explicit ideal use cases ('social cards, certificates, tickets, OG images') and explains the two invocation modes: raw html or template + data. It does not explicitly name sibling alternatives or when to choose html_to_pdf or screenshot_url instead, so it misses clear exclusions.

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