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

With no annotations, the description carries the full behavioral burden. It adds real value by noting the output includes a table of contents and that file_url must be a public URL, but it omits permissions, rate limits, failure modes, or what the conversion produces beyond the TOC note.

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 terse lines, front-loaded with the purpose and then the two parameters. Every sentence contributes information with no repetition of the tool name.

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 not be described, and both parameters are covered in the prose. The main remaining gap is the absence of any behavioral detail an unannotated conversion tool might warrant, but for this simple two-parameter converter it is close to sufficient.

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 0%, so the description must compensate, and it largely does: it defines file_url as a public FB2 URL (a meaningful constraint beyond 'string') and spells out the page values a5 (default, book-like) and a4. Enum values and the default semantics are conveyed in prose.

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 states a specific verb and resource pair — converting an FB2 book into PDF — plus a distinguishing output feature (a generated table of contents). This clearly separates it from generic converters, though it never names the format-specific siblings (epub_to_pdf, djvu_to_pdf) it is adjacent to.

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 format pair rather than stated: an agent can infer this is the tool for FB2 sources, but there is no explicit when-to-use, no prerequisites, and no pointer to alternatives for other ebook formats.

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