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

Annotations already cover the safe-read profile (readOnly, idempotent, non-destructive, openWorld), so the description's added value is the deterministic chunk_id format (lang:slug:chapter:para) and chunk stability, which matter for caching/indexing. It does not discuss rate limits or pagination semantics beyond the schema fields, so a 4 rather than 5.

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 purpose, then labeled When/Do-not/Returns blocks. Dense but every clause carries routing or payload information; nothing is redundant filler.

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?

No output schema exists, but the description enumerates the return object (lang, slug, title, license, corpus_version, total_chunks, chunk fields), so an agent knows both how to call it and what comes back. Nothing material 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 limit, start, chapter and max_chars are fully documented in the schema itself. The description adds no parameter-level detail beyond the return payload shape, making the baseline 3 correct.

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 phrase ('Stable paragraph-level chunks for one book') and immediately qualifies it against sibling tools (whole chapters vs. cross-book search). An agent can distinguish it from cyberlibrary_get_chapter and cyberlibrary_fulltext_search without opening either 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?

Explicit 'When to use' and 'Do not use' sections, each naming the alternative tool that covers the excluded case (cyberlibrary_get_chapter, cyberlibrary_verify_quote/cyberlibrary_fulltext_search). Routing is unambiguous.

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