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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the safety profile is covered by structured data. The description adds that it returns the result file (useful, since there is no output schema), but 'print it right away' implies a printing action the tool does not perform — it only returns a file, which is mildly misleading. It also never explains what the default split (50%, horizontal, keep both) actually does to the document.

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 short sentences with the core action front-loaded, no filler. The only weak sentence is 'print it right away', which adds an unsupported claim rather than useful 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 file-transformation tool with full schema coverage and no output schema, the description covers format acceptance and return type but omits the behavior of the five options and mischaracterizes the output as printable. Since the schema carries the parameter burden, the remaining gap is the missing explanation of default cut behavior and the pages/rotate semantics.

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 schema already documents files, upload_id, content_base64, and the 50 MB limit, making 3 the baseline. The description's 'cut in the middle' loosely conveys the default at=50 and cut=horizontal, but says nothing about the at, cut, keep, pages, or rotate options that materially change the output. Marginal value beyond the schema.

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 concrete verb and resource: cut an A4 parcel label in the middle, producing a halved PDF. The 'parcel label' niche distinguishes it functionally from the generic split-pdf and crop-pdf siblings, though it never says so explicitly. An agent can infer the purpose but must reason about why halve-pdf exists alongside split-pdf.

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?

Usage is implied by the 'A4 parcel label' framing rather than stated: use this for shipping labels, not general PDF splitting. There is no explicit when-to-use/when-not, no mention of split-pdf or crop-pdf as alternatives for other cases, and no prerequisites mentioned. An agent must infer the routing decision.

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