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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: cost is zero, no API key is required, and auth method/links are surfaced in the response.

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 that are front-loaded with the call-order guidance and then cover inputs, output, and cost. No filler, no restatement of the tool name.

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, so the description must describe the return value, and it does: a JSON listing of tools, input modes, page sizes, per-plan limits, auth method, and links. For a zero-parameter discovery tool, nothing an agent needs 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?

The tool takes zero parameters, which is the baseline-4 case; the description confirms this explicitly with "Inputs: none," eliminating any doubt about whether filtering or scoping arguments exist.

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 and resource (list Rendlet capabilities) and adds scope the name alone doesn't convey: what can be rendered and which tools are free. An agent can distinguish it from siblings like get_pricing, html_to_pdf, or render_template 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?

"Use first" gives an explicit ordering cue for when to call it, which is stronger than implied usage. It stops short of naming alternatives or exclusions, and it doesn't address the overlap with the sibling get_pricing despite both covering cost information.

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