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

Annotations already indicate readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so safety and side-effect expectations are covered. The description adds only the ordering behavior and does not discuss output creation or file handling, but no contradiction exists and the schema covers input constraints.

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 a single sentence of about 13 words, front-loaded with the action and object. Every word contributes, and it is appropriately sized for a low-complexity tool.

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?

The tool has only one parameter with full schema documentation, annotations cover the behavioral profile, and an output schema exists. The description plus schema together provide enough for correct invocation; only minimal behavioral elaboration is delegated to the output schema.

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 coverage is 100%, so the baseline is 3. The description's 'in the given order' reinforces the files array ordering already documented in the schema ('in the order to merge them'), but adds no new parameter-level semantics.

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 uses the verb 'Merge' with the resource 'PDF files' and specifies the result 'a single document' plus the ordering constraint 'in the given order.' This clearly distinguishes it from sibling operations like split_pdf, rotate_pdf, and extract_pages.

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?

'Merge several PDF files' implicitly tells an agent this is for combining multiple PDFs, and 'given order' clarifies the intended use case. It does not explicitly name alternatives or exclusions, but the sibling list and wording make the selection obvious.

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