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

Annotations already declare idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: it clarifies *what* idempotency means here ('attaches to the same render rather than repeating it') and notes that plan limits apply as in the web app, warning of a possible failure mode. It stops short of describing auth, rate limits, or what the job object contains.

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 short sentences, each carrying distinct information: what it does, the polling target, the when-to-use routing, idempotency semantics, and the plan-limit caveat. The core action is front-loaded with no filler.

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, the description usefully explains that the return is a job handled via get_export_status. For a one-parameter, non-destructive, idempotent render tool this is nearly complete; the only real gap is the unexplained projectId.

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 0% for the single required parameter, and the description never explains projectId — the agent must infer that it identifies the ebook to render. The phrase 'existing ... ebook' hints at it, but no format, source, or validation detail is added beyond the schema's minLength/maxLength.

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 ('Render an existing Unplain ebook to PDF') plus the return shape ('return a job to poll with get_export_status'). It also distinguishes itself from the sibling create_ebook by scoping to an *existing* ebook, and names get_export_status as the follow-up.

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?

Explicitly says when to call it ('Use this after update_ebook') and what not to do instead ('instead of creating the ebook again'), which directly routes the agent away from create_ebook. The polling follow-up via get_export_status is also spelled out, closing the loop.

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