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

The description goes beyond annotations (readOnlyHint false, idempotentHint true) by detailing mutation behavior, the local-seconds coordinate system, the replacement of entrance/exit animations, the clearing mechanism, and the limitation on subject-matted text. It also notes the return of project identity, which is not in the schema. No contradiction with annotations.

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?

The description is dense and front-loaded with the project-scoped warning, then the core action, followed by important details. Every sentence contributes to usage, behavior, or constraints. It's slightly long but not verbose, and the structure guides the agent from scope to action to caveats.

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 tool with no output schema, the description covers all critical aspects: target object type, scoping, coordinate semantics, replacement behavior, clearing behavior, and a key limitation. It also mentions the return of project identity, which is essential for chaining. An agent has enough context to call it correctly.

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 75% and already includes a detailed description of the motion parameter. The description adds valuable semantics: explains that curves use LOCAL seconds, which affects how timing works, and clarifies that passing an empty object clears the curve. This exceeds the schema's coverage, so it earns above baseline.

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 clearly states the verb ('Set or replace') and the resource ('coherent x/y/scale/rotation/opacity keyframes on an EXISTING ordinary text item'). It distinguishes itself from sibling tools like set_overlay_motion by explicitly targeting text items and mentioning it replaces named entrance/exit animation. The purpose is unambiguous.

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?

It provides clear usage context: acts on existing text, is project-scoped, and replaces named animations. It also gives an explicit instruction for clearing motion (pass motion={} or omit). However, it doesn't explicitly contrast with alternative motion tools like set_overlay_motion, and the only exclusion mentioned is subject-matted text. Overall, the guidance is strong but not exhaustive.

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