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

Even though annotations already indicate non-destructive and non-read-only behavior, the description adds substantial detail: the source render is left untouched, error handling for out-of-range pages, the return format {renders: [...], count}, and integration with sibling tools. This goes well beyond the annotations.

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?

The description is three sentences, each earning its place: definition and inverse, usage examples, and behavioral/auth/return details. No redundant or filler content.

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?

Given the tool has 2 parameters (100% schema coverage), no output schema, and moderate complexity with nested arrays, the description compensates fully by specifying return format, error atomicity, auth requirements, and compatibility with sibling tools. No significant gaps remain.

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?

With 100% schema coverage, the baseline is 3. The description adds value by explaining that omitting a range's 'to' runs to the end, that a range starting past the last page fails the entire call, and that outputs are returned in the same order as ranges. These nuances are not fully captured in 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?

The description clearly states the tool extracts page ranges from a render into new PDFs and explicitly identifies it as the inverse of merge_pdfs, providing a specific verb and resource with direct sibling differentiation.

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 contrasts the tool with merge_pdfs and gives concrete usage examples (halving a contract, peeling off single pages). It does not explicitly state when not to use it or list all alternatives like edit_pdf, but the context is clear and helpful.

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