list_libraries

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

No annotations exist, so the description carries the full burden, and it does disclose non-obvious behavior: the source-kind values (full-text / index-only / readme), the 'unknown' fallback for uncached or legacy metadata, and the '[resolved]' marker meaning auto-resolution from npm/PyPI. It omits any note on ordering, pagination, or freshness of cache status, which is a minor gap for a read-only listing tool.

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?

A single dense sentence front-loads the core purpose before qualifying the fields, and the closing sentence gives the next action. Every clause earns its place by defining an otherwise ambiguous output token (full-text / index-only / readme / unknown / [resolved]).

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 output schema, the description must explain the return shape, and it does: entries carry cache status, source kind with its enum values and unknown case, and the [resolved] marker. It does not describe ordering or how many entries come back, a small remaining gap for a listing 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 the baseline is 4 and there is no parameter surface the description could or should explain. The clause about source kind is output semantics rather than parameter meaning.

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 the libraries this server can fetch docs for) and immediately qualifies what each entry contains: cache status and source kind. It also names the sibling get_docs for the retrieval step, so an agent can separate listing from fetching 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?

Explicitly routes the agent: 'Use get_docs to retrieve content,' which is the natural follow-up action. It does not state when-not to use this tool or mention resolve_library/search as related alternatives, so it stops short of full when/when-not guidance.

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