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

Annotations already declare it is a non-destructive write operation in a closed environment. The description adds that it accepts PDFs and returns a result file, but does not clarify what happens to input files, error behavior, or the exact return format. With annotations covering the safety profile, this minimal additional context merits a 3.

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?

Two short sentences with zero waste, front-loading the core action before the input/output summary. Every sentence earns its place.

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?

The tool is simple and the input schema is fully described, but there is no output schema and the description only vaguely says 'Returns the result file' without specifying the return format (e.g., base64, URL, file object). This is a meaningful gap for an agent consuming the result.

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 the schema fully documents the 'files' parameter including name, upload_id, and content_base64. The description only restates that it accepts PDFs and adds no parameter-specific details beyond the schema. Baseline 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?

States a specific verb ('Combine') and resource ('PDF files into one document'), making the operation unambiguous. The action is clearly distinct from sibling tools like split-pdf or reorder-pdf, so an agent can identify its role without ambiguity.

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 purpose implies when to use it (when PDFs need to be merged), but there are no explicit guidelines about alternatives, prerequisites, or when not to use it. Usage is implied rather than stated.

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