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

Goes well beyond the annotations by disclosing per-file limits (25 MB / 500 pages), the return artifact (download_url valid 24 hours) with size and page count, and the billing model (1 credit, 5 free calls/month). Those are exactly the operational facts an agent needs before committing to a call.

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 short sentences, front-loaded with the action and result, then input contract, then output and cost. No filler; every clause carries information.

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 one-parameter tool with an output schema, this covers action, input format and constraints, output artifact, and cost. Nothing an agent needs to call it correctly is missing.

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 0%, so the description must carry the load, and it does: it defines the single argument as a list of base64-encoded PDF contents, states per-item size/page limits, and notes that list order determines merge order. Only the maximum number of files in the list is left unstated.

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 and resource (merge PDFs into a single PDF) plus the ordering semantics of the output. Unambiguous against siblings like images_to_pdf or pdf_tables_to_excel, though it never names them to reinforce the distinction.

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?

Usage is implied by the input description (a list of base64 PDFs, merged in order), and the cost/limit notes hint at when it is appropriate. There is no explicit 'use this instead of X when Y' routing or stated preconditions beyond format.

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