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

Annotations declare readOnlyHint=true and openWorldHint=false, and the description adds the operational cost of 30 points per call, which is useful beyond the schema. It also says the PDF is converted and returned, but it does not describe failure behavior, output representation, or other side effects; the readOnlyHint is not contradicted because no persistent state modification is claimed.

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 compact and front-loads the core action before the cost note. The Korean sentence is partly redundant with the English opening but also adds the explicit 'returns' behavior in a bilingual interface, so the structure remains efficient.

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 single-parameter conversion tool with no output schema, the description covers the conversion semantics, the input restriction, and the cost, which is most of what an agent needs. It lacks an explicit return-format statement and alternative routing, but those are minor given the tool's simplicity and the complete schema.

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?

With 100% schema description coverage, pdf_url is already documented as a downloadable HTTPS URL with application/pdf content type and a 25MB limit. The tool description adds no parameter-level meaning beyond repeating the PDF restriction, so the baseline of 3 applies.

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 opens with an explicit verb and both target formats: 'Convert a PDF file to a DOCX (Word) file,' and the Korean sentence repeats the same transformation. This makes the conversion direction unambiguous and separates it from the sibling docx_to_pdf without needing to inspect the schema.

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 conversion direction strongly implies when the tool should be used (PDF input, DOCX output), but the description never states it explicitly or names alternatives such as docx_to_pdf for the reverse direction. It only gives the input constraint that PDF files are allowed, which is a prerequisite rather than usage guidance.

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