List Engine DJ libraries

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it re-scans on every call (not cached), explains that engine://libraries is a start-time snapshot, and discloses that unreadable libraries remain listed with status 'unreadable' and an error set. This is exactly the kind of behavioral disclosure that helps an agent predict side effects and state.

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 three sentences, each earning its place: scope, re-scan behavior, and unreadable-library behavior. The most important fact (lists every discovered library) is front-loaded, and the follow-up guidance about passing uuid/path to other tools is a natural, useful extension. No filler or repetition of schema/annotation content.

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?

For a zero-parameter, read-only, idempotent list tool, the description is complete. It covers what is listed, the freshness semantics, the failure behavior, and how the results should be used with sibling tools. There is no output schema, but the description's mention of status and error fields gives the agent enough expectation of the return shape. Nothing an agent needs to call this correctly 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?

The tool has zero parameters, so the schema provides no parameter semantics. The description compensates by explaining how the output (listed uuids/paths) feeds into other tools' `library` argument, which is the only parameter-related context an agent needs. Baseline 4 for zero-param tools is appropriate; no deduction needed since there are no parameters to document.

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 states a specific verb ('List') and resource ('every discovered library'), and explicitly distinguishes itself from a start-time snapshot resource (engine://libraries). It also clarifies that unsupported-schema libraries are included, which differentiates it from sibling tools that operate on supported libraries.

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?

The description explicitly explains when to use this tool: to see libraries discovered since server start, including unsupported or currently unreadable ones. It also provides routing guidance for other tools, telling the agent to pass a listed uuid or path as the `library` argument, and notes the fallback behavior when no library is passed. This is clear usage context with no ambiguity.

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