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

Even though annotations already mark the tool as read-only and idempotent, the description adds rich behavioral detail: it returns verbatim text with `[p. N]` markers, `path`, `url`, and `truncated: true` with `next` when the window doesn't fit. This is exactly the kind of non-obvious behavior an agent needs beyond annotations.

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 front-loaded with the core purpose, then gives parameter guidance, then output/return behavior, then an alternative. Every sentence earns its place and there is no filler or repetition of the schema.

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?

Given that there is no output schema, the description fully covers return values, pagination via `next`, truncation behavior, and alternative tool routing. It is complete enough for an agent to invoke the tool correctly with any of the valid parameter combinations.

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 carries the full burden of explaining parameters. It explains `document_id`, `page_from`, optional `page_to`, `article` (with concrete examples like 'Art. 15' and 'único'), and `max_chars` with its 40,000 cap and default. No parameter is left unexplained.

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 a specific verb and resource: 'Read part of a long document: a range of pages, or one article.' It also clearly distinguishes this tool from `search`, which is for finding a phrase rather than paging through the document.

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?

It explicitly states when to use which parameters: pass `document_id` with either `page_from` (optionally `page_to`) or `article`. It also names an alternative: 'To find a phrase in a long document instead of paging through it, use `search` with its `document_id`.' This leaves no ambiguity about selection.

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