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

Annotations declare readOnlyHint=false and the description consistently states WRITE, so no contradiction. Beyond annotations it adds genuinely useful behavioral context: the call is project-scoped, acts only on the explicit project_id, and returns the project identity with its result. It stops short of disclosing reversibility or what happens to pre-existing motion on re-aim.

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?

Front-loads the two constraints that matter (PROJECT-SCOPED, WRITE) before the effect narrative, and packs the media/effect detail into a single dense sentence. Slightly run-on, but every clause carries information.

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 9-param write tool with no output schema and sparse schema descriptions, the definition covers scope, operation type, and return identity but leaves most tuning parameters (fit, ease, amount, focus coordinates, treatment) unexplained. Adequate to understand intent, insufficient to invoke confidently with non-default parameters.

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 only 11% across 9 params, so the description must carry the load. It does map several path behaviors (push/pull toward a detected face, pan a panorama, rise a tall scan, drift), which gives semantic meaning to the path enum, but fit, ease, amount, focus_x, focus_y, and treatment remain entirely undocumented in both schema and description.

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: a still photo (cover image overlay, image insert, moving still) gets motion via push/pull, pan, rise, or drift. It is concrete enough to separate from generic siblings like set_overlay_motion or add_zoom by naming the input media type and effects, but it never names an alternative tool, so the differentiation is implicit rather than explicit.

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 describes what gets animated (a photo sitting dead still, a cover overlay, an image insert) but gives no when-to-use vs alternative guidance, no prerequisites, and no exclusions. A sibling set containing set_overlay_motion, add_zoom, add_zoom_path, and add_kinetic_text demands explicit routing that is absent here.

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