Merge PDFs into one file

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

With no annotations, the description carries the full burden. It discloses key behaviors: 'Page sizes are kept as-is', 'Inputs are never modified', and 'Free tier: up to 5 files per merge'. It does not mention error handling or output details, but these are less critical for a merge operation.

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 concise, consisting of three sentences that cover purpose, behavior, and constraints without unnecessary details. It is well-structured and front-loaded with the primary action.

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 simple merge tool, the description provides enough context for an agent to call it correctly: it specifies the order, the output file, and the free tier limit. It lacks details on error conditions or file format specifics, but these are not essential for a basic operation and the schema covers parameter-level details.

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% for all three parameters (paths, out_path, overwrite). The main description does not add additional meaning beyond the schema; it only reinforces the order for paths. Since the schema fully documents each parameter, the baseline score 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 tool's purpose with the verb 'join' and the resource 'PDFs', specifying that it combines several PDFs into one in the given order. This distinguishes it from sibling tools like pdf_split, pdf_rotate, or pdf_stamp.

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 gives clear context by saying 'Call this tool to join several PDFs into one' and notes the order of files. However, it does not explicitly compare with alternatives or state when not to use it, though the purpose is sufficiently distinct from siblings like pdf_split.

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