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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds real value beyond that: it discloses the project-scoping behavior ('acts only on the explicit project_id and returns the project identity with its result') and that the response carries purpose, params and sound cues, though it says nothing about pagination or result size.

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?

Three front-loaded labeled clauses (PROJECT-SCOPED, READ, Call once) with no filler, and the action/constraint ordering is sensible. The parenthetical inventory of template types is long but earns its place by telling the agent what the library contains.

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 compensates by describing what each entry contains and the returned project identity. Annotations cover the safety profile. Only pagination/volume behavior is left unstated, which is a minor gap for a read-only two-parameter lister.

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 baseline is 3. The description reinforces project-scoping and implicitly enumerates the category families that the category filter accepts, but the schema already documents both parameters including the enum-like category list, so the description adds little beyond 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 (READ/list) and resource (the premium motion-graphics library), and enumerates the template families covered (animated titles, counters, callouts, charts, transitions, textures, CTAs). This cleanly separates it from sibling listers like list_music_library, list_sound_library and list_assets.

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 an explicit sequencing rule — 'Call once before designing motion beats' — which tells the agent when in the workflow to invoke it. It does not name the alternative tools (e.g. add_motion_graphic/set_motion_graphic) that consume these templates, so routing guidance is strong but not complete.

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