Merge PDFs

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

Goes well past the annotations, which only declare destructiveHint=false and idempotentHint=false: it discloses the output naming rule, the default output location, that existing files are never overwritten, and that inputs are left unchanged. That is exactly the side-effect information an agent needs before calling a write tool.

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?

Three tight sentences, front-loaded with what happens and followed by naming, destination, and non-destructive guarantees. No sentence is redundant with another.

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?

An output schema exists so return values need no explanation, and the description still covers naming, destination, overwrite protection, and input preservation — everything needed to invoke a merge correctly without surprises.

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 both params are already documented, including ordering and the output_path existence constraint. The description adds one genuinely new fact — the -merged suffix derived from the first file — but otherwise restates schema content, which is the baseline-3 case.

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?

States a specific verb ("combines") and resource (PDFs) plus the ordering semantics in the first clause, which immediately separates it from split_pdf, extract_pages, and reorder_pages in the sibling set.

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?

Clear operational context — you merge multiple PDFs into one — and no other sibling performs this operation, so no explicit alternative needs naming. However, it never states a when-to-use condition or any exclusion (e.g. single-file input, encrypted PDFs), leaving the agent to infer.

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