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

Annotations only cover the safety profile (readOnly, idempotent, non-destructive); the description adds genuinely new behavior: the credit formula ceil(pages/20) with a minimum of 1, the accepted input encodings, the return shape, and the fallback signal (meta.note) for PDFs with no text layer. That is cost, encoding, and edge-case disclosure well beyond structured fields.

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?

Front-loaded with the purpose, then cost, input, and output in compact fragments; every piece carries information. The telegraphic 'File input (file): ... Output: JSON. {...}' style is dense but not padded, costing only a little readability.

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?

With no output schema, the description compensates by spelling out the return structure ({page_count, pages, chars}) and the no-text-layer note, plus pricing and accepted input forms. Nothing needed to call this three-parameter tool 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 description coverage is 100%, so the schema already documents 'file', 'pages', and 'layout'. The description restates the same input formats and page-range idea without adding syntax or constraints the schema lacks (e.g., 10 MB cap lives only in 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 and resource ('Extract the text of a PDF page by page') and immediately names its two distinguishing capabilities (page selection, layout-preserving mode). An agent can separate it from pdf_info, pdf_merge, and pdf_split without opening any 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?

Usage is implied through the feature list and the credit-cost formula, which nudges toward narrow page ranges, but there is no explicit when-to-use statement and no named alternative (e.g., pdf_info for metadata only). A reader must infer the selection criteria.

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