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

Annotations already declare read-only, idempotent, and closed-world behavior, and the description adds meaningful context beyond them: the simulation basis and the exact categories of state returned. It also discloses important scope limits, though it still omits execution cost or pagination behavior for the returned samples.

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 tightly packed sentences front-load the return value list and then add the key limitation. There is no redundant restatement of the title or wasted preamble.

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?

The enumerated return values help compensate for the absence of an output schema. However, the required document parameter is an untyped nested object with no schema description, and the description does not explain its expected structure or source, leaving a significant setup gap for an agent invoking this tool.

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%, so the schema already documents bodyIds, duration, and sampleInterval defaults/ranges. The description only adds that parameters must be numeric, which is vague and arguably misleading for bodyIds/document, and does not clarify the required document object. Baseline 3 is appropriate given the high schema coverage.

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 states a specific action (analyze motion), the computational basis (web physics engine and parameter timeline), and the returned quantities (position, velocity, acceleration, force, contact, spring state, sampling stage). It does not explicitly contrast with siblings like preview_scene or inspect_scene, but the motion-analysis resource is clearly distinct.

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 gives a useful negative boundary: parameters must be numeric and this is not symbolic solving or an infinite-time-domain analytic solution. However, it does not say when to choose this over preview_scene/inspect_scene, nor does it state prerequisites such as needing a document produced by build_scene.

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