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

Goes well beyond the annotations by disclosing quota consumption per successful call, that nothing is stored, and that over-quota or invalid input surfaces a tool error with an explanation. These are exactly the operational facts an agent needs before invoking, and they do not conflict with readOnlyHint=false / idempotentHint=true.

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 tight sentences: what it renders, what it returns, and the operational caveats. Zero filler and the source constraint is front-loaded before the quota detail.

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 eight parameters, nested options, and no output schema, the description still covers return format (base64 embedded resource), input mode rules, and failure behavior. Nothing an agent needs to call it correctly 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 88%, so parameter-level descriptions largely come from the schema. The description still adds the critical mutual-exclusivity rule across the five source parameters, which the schema does not encode, making it more than a restatement.

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 (Render) and resource (PDF) and immediately constrains the input modes, which cleanly distinguishes it from render_image and the template CRUD siblings. An agent knows exactly what this tool produces.

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 makes the key usage rule explicit: exactly one source among html, markdown, url, template(+data) or template_id(+data). It does not, however, say when to prefer render_pdf over the sibling render_image, so context selection is left to inference.

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