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

The description explicitly states 'Read-only,' but the annotations declare readOnlyHint=false. This contradicts the annotations. Although the description adds useful behavioral details about unreadable files and the total count, the contradiction with the structured annotation is a serious inconsistency and forces the lowest score.

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-loaded: the core behavior, output type, and failure handling are all stated in three short sentences. There is no filler or redundant restating 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?

For a simple one-parameter tool, the description covers the main behaviors: per-file page count, total pages, readable count, and handling of unreadable files. It lacks an explicit output format or prerequisites, but the schema and sibling context cover most practical needs.

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 the schema fully documents the 'paths' parameter as an array of PDF names uploaded with pdf_upload. The description adds context about counting multiple files and handling unreadable ones, but does not add new parameter-level semantics beyond what the schema already provides.

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: it counts pages in PDFs, reporting page count per file plus a total and readability count. This clearly differentiates it from siblings like pdf_info or pdf_pages, which serve different purposes.

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 description implies the tool is for counting pages across any number of PDFs, and mentions that unreadable files are still reported. However, it does not explicitly specify when to use this tool versus alternatives like pdf_info or pdf_merge, nor does it state exclusions.

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