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

Annotations cover the safety profile (readOnly=false, idempotent=false, destructive=false), and the description adds genuinely non-obvious behavior: project scoping with returned identity, occluders=[] drawing over people, shadow=true allowing real shadows to darken, and blend=multiply printing into the surface. This is substantive context beyond the structured fields.

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?

Dense but front-loaded: the scoping constraint comes first, followed by the core action and the modifier semantics. Every clause carries information, though the final sentence is a long run-on packing three behaviors together.

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 14-parameter mutation tool with no output schema, the description covers the essential mental model (what gets placed, where, how it composites) and notes the project identity is returned. The undocumented id/start/end/place params keep it short of fully 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 coverage is only 7%, so the description must compensate and largely does: it explains quad geometry (4 corners TL,TR,BR,BL as program fractions), t, motion_id, text, occluders, shadow, blend, and the project_id scoping rule. It leaves id, start, end, place, and plane semantics unexplained, which are real gaps, but the added meaning for the geometry and blending params is strong.

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 and resource: pin a graphic (motion_id) or text onto a plane/quad surface at time t. This distinguishes it reasonably from overlay-style siblings, though it never names an alternative tool directly. Purpose is unambiguous without opening the schema.

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 implies when it applies (laying a graphic or words on a physical surface in the scene) but gives no explicit when-to-use versus alternatives such as place_in_world, add_text, or set_overlay_motion. The PROJECT-SCOPED note is the only real routing guidance.

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