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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known; the description adds the key behavioral detail that nothing is persisted and no pixels are rendered. It does not mention non-determinism despite idempotentHint=false, which would be useful since drafting from a prompt likely varies across calls.

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?

Two tight sentences with no filler; the generation action comes first and the non-persistence caveat follows. Every clause earns its place.

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 not be explained, and the 'does not save or render' note covers the main ambiguity. However, for a drafting tool in a crowded animation toolset, the missing link to create_mockup_animation and any prompt-shaping guidance leaves the definition only minimally complete.

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 description coverage is only 33% — only deviceKind is documented, and the description adds nothing about it. The two required parameters (prompt, projectId) are never discussed, so the description gives no guidance on what kind of motion prompt to write despite the 3–600 character constraint.

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 uses a specific verb and resource ('Drafts mockup keyframe data from a motion description') and clearly states what the output is and is not. It does not name or distinguish itself from close siblings such as create_mockup_animation, preview_mockup_animation, or update_mockup_animation, so an agent must still infer the boundary.

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?

Saying it 'returns configuration data without saving an animation or rendering video pixels' implies a generate-then-create workflow, but the description never says when to pick this over create_mockup_animation or that its result feeds into it. Usage is only implied, not stated.

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