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

Annotations already convey that this is a mutating (readOnlyHint=false) but non-destructive and idempotent operation. The description adds the behavior of preserving input order, which is useful but not extensive. No side effects, permissions, or limits are disclosed beyond what annotations provide.

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, concise sentence that captures the core functionality without any fluff. It is front-loaded with the action and result, making it immediately scannable and easy to parse.

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 straightforward merge tool with well-defined parameters and no output schema, the description covers the essential behavior. It does not mention edge cases like file size limits, but the schema handles constraints (minItems, maxItems, maxLength). Overall, the information is sufficient for an agent to use it correctly.

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 both parameters (files and output_filename) are fully documented in the schema. The description's mention of order mirrors the schema's own statement about file order, adding no new meaning. Baseline of 3 is appropriate.

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 verb 'Combine' with resource 'PDFs' and specifies the output is a single PDF, while also emphasizing order preservation. It distinguishes from sibling operations like split, remove, or reorder, making its purpose unambiguous.

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 implies when to use it: whenever two or more PDFs need to be combined into one. It provides clear context but does not explicitly mention exclusions or alternatives. However, the tool's purpose is so specific that an agent would naturally select it for merging tasks.

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