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

With no annotations, the description provides some behavioral traits: 'pure local operation' (no network), 'failure auto refund' (safe). However, it does not disclose whether the operation is destructive, what happens to original files, or any authentication requirements.

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 extremely concise: a single sentence clearly stating purpose, cost, and behavior (local, auto-refund). Every word is necessary; no fluff.

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 with complete parameter schemas and no output schema, the description is nearly complete. It missing details on where the output file is saved, but the system context likely implies the staging area.

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 baseline is 3. The description adds value by specifying that file_ids must come from the uploaded file staging area, must be in order, and require at least 2 files. The optional filename is also mentioned.

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 merges multiple PDFs into one file in order, with a specific verb and resource. It distinguishes from sibling tools like pdf_split, pdf_compress, and pdf_organize by focusing exclusively on merging.

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 usage for merging PDFs but lacks explicit guidance on when not to use it or how it compares to alternatives like pdf_organize. No exclusions or context for when to prefer other tools.

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