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

Annotations (readOnlyHint=false, destructiveHint=false, idempotentHint=false) describe the safety profile without contradiction, and the description adds genuinely new context: the operation is free, it returns a new artifact_id plus a download_url, and that link expires in about an hour. That expiry detail is the kind of operational trait annotations cannot convey. It stops short of covering size or source-count limits.

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?

Front-loaded and otherwise efficient, but the core instruction is duplicated verbatim-ish ('Join whole PDFs into one file in the order given. Join whole PDFs in order:'), which wastes a full sentence. Removing the repetition would lose no information.

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?

For a single-parameter tool with an output schema, the description covers purpose, ordering semantics, parameter shape, return values, link lifetime, and sibling routing. What remains unstated are practical limits (maximum source count, size caps) that an agent might need before calling.

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% and the schema itself documents nothing about sources, so the description carries the load by defining it as 'a list of {artifact_id}' and stressing that order matters. The one gap is that the schema allows additionalProperties on each item, implying possible fields the description never mentions.

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 ('Join whole PDFs into one file') and explicitly scopes to whole-file merging rather than page-level work, naming the sibling compose_pdf as the alternative. An agent can distinguish this from compose_pdf and extract_pages without opening either 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?

Explicitly routes the agent: whole PDFs go here, and 'For page selections use compose_pdf' names both the when-not condition and the alternative tool. This is the exact when/when-not/alternative pattern the rubric rewards.

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