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

Annotations already declare readOnlyHint=true and idempotentHint=false, and the description reinforces both: 'Reads or computes only and changes nothing' and 'each call is charged, so repeats are not free' explains why the call is not idempotent. It goes well beyond annotations with size limits, failure modes that are billed at zero (scanned PDFs, encrypted files, non-PDF URLs), arXiv abstract-link handling, and full pricing/auth mechanics.

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 core action, output, and limits, then failure modes, then pricing. It is on the long side and the charging point is made twice ('Price $0.005/call' and 'each call is charged, so repeats are not free'), but nearly every sentence carries operational value.

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 four-parameter read tool with no output schema, the description covers return contents, pagination controls, size and page caps, per-failure-mode behavior, and cost/auth. An agent has everything needed to decide to call it and to interpret 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 baseline is 3. The description restates the page-window concept ('Choose a first page and how many pages to read (up to 200)') and that maxChars caps output, but adds little syntax or default behavior beyond what the schema already documents for each parameter.

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?

Opens with a specific verb+resource: 'Extract the text of a PDF from its URL', and states the output shape (page-by-page text plus title, author, page count, character counts). This clearly separates it from generic siblings like 'extract', 'contents' or 'summarize', which would not necessarily return raw PDF text.

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?

Gives concrete use cases ('read papers, invoices, reports and manuals into an agent') and a worked example URL, plus explicit constraints (public PDF, up to 10 MB, 200-page cap) and failure conditions. It does not explicitly compare itself to sibling tools such as 'extract' or 'contents', so an agent must infer the routing rather than being told.

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