library_apply

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

With no annotations supplied, the description carries the full behavioral burden and does so: it declares the operation undoable, spells out the pipeline (package download, MD5 verification, import, default scene placement), states it blocks until the object appears in the scene, and clarifies that AI image / AI makeup kinds only download existing results with no regeneration and no credit consumption. That is exactly the permission, side-effect and cost information an agent needs before a mutating call.

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 paragraph where each clause carries real information (pipeline, kind dispatch, return shape, prerequisite, verification). The return-value detail and the prerequisite are somewhat back-loaded rather than front-loaded, which slightly hurts scanability.

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, and the description compensates by naming the response fields (kind, added_objects with object names and object_path, package_folders). Combined with the kind-specific behavior and the pre/post-step guidance, nothing an agent needs to invoke 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?

Schema coverage is 100%, so the schema already documents all five parameters; the description adds the session-scoped provenance requirement for template_id and reinforces the kind=package constraint on auto_instantiate. It does not add new syntax or edge cases beyond that, but it does more than restate the schema.

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 ('apply an official asset to the target project') and anchors it to a familiar UI action ('same as clicking Apply in the library panel'). It also distinguishes this tool from the sourcing siblings (library_list / library_search) and from music_apply by scoping itself to official material and plaza cards.

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?

Gives a hard prerequisite ('template_id must come from this session's library_list / library_search') and a follow-up step ('use capture_preview to verify'), plus explains that plaza cards dispatch by kind. It stops short of an explicit exclusion such as when to prefer music_apply or aweme-style flows, so it is strong but not a full when/when-not map.

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