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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds value by disclosing the return shape ('a flat map of named endpoint URLs plus version and citation guidance'), which no annotation or output schema supplies.

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 cleanly segmented into When to use / Do not use / Returns. The endpoint enumeration is long but each item is a distinct capability an agent may want to discover; slight verbosity keeps it from a 5.

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 parameters, no output schema, and annotations carrying the safety profile, the description covers the essentials: what it returns, when to call it, and when not to. Key names inside the returned map are not specified, but that is a minor gap for a discovery tool.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. No schema-level parameter semantics are needed.

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+resource ('Discovery endpoints for Cyber Library') and enumerates exactly what it exposes (MCP endpoint, tools list, Server Card, catalog API, OpenAPI, search UI). It is immediately distinguishable from the sibling book-data tools like cyberlibrary_get_chapter or cyberlibrary_search_books.

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?

Explicitly provides both directions: 'When to use: you need a machine-readable entry point or want to know what else this service exposes' and 'Do not use: for book data itself.' The negative guidance routes the agent away from the entire cyberlibrary_* book family without ambiguity.

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