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

Annotations already cover read-only, idempotent, and closed-world safety, and the 'once is enough' note largely restates idempotence. The description earns credit beyond that by explaining that `capabilities.retrieval_mode` reports whether semantic retrieval is actually available, warning that `lexical` means synonym rephrasing may fail — a meaningful behavioral caveat the annotations cannot express.

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-loads the purpose, then uses labelled sections for when-to-use, when-not-to-use, and the return-value caveat. Every sentence is doing work, though the markdown bolding and multi-section layout make it slightly heavier than the small scope requires.

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?

An output schema exists, so return values need no explanation, yet the description still flags the one return field whose meaning affects downstream behaviour (retrieval_mode). For a zero-parameter discovery tool this leaves nothing an agent needs ambiguous.

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 the baseline is 4. The description still adds a little value by framing what the returned filter metadata is intended to support (department/type/time filtering), but there is no parameter semantics to clarify.

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 (list knowledge bases) and then explicitly enumerates the three things returned: filters' supported fields, value domains, and the instance's retrieval capability. This clearly separates it from the sibling `search`, which does the actual querying.

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?

Provides explicit 'when to use' (unsure which libraries exist, or before filtering by department/type/time) and 'when not to use' (you already know what to look for → go straight to `search`), naming the alternative directly. It even caps invocation frequency with 'once is enough'.

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