assign_motion_path

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

Annotations only declare readOnlyHint=false and openWorldHint=false, so the description must carry the rest. It does add real behavioral context by disclosing that setting animateMs implicitly creates a progress animation from 0 to 1, which is a side effect an agent would not otherwise predict. It says nothing about what happens to an existing followPath binding on the layer, whether the operation is undoable, or what a revision conflict looks like.

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?

Three short sentences, each front-loading the primary action first and then the two most consequential options. No filler, no restatement of the name, and the jargon term (followPath) is placed in parentheses as a parenthetical rather than dominating.

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 10-parameter mutation with no output schema, the description covers the core semantics and the one non-obvious side effect (auto-animation). The remaining gap is the optimistic-concurrency and session parameters, which are entirely undocumented in both schema and description and could matter on a write operation.

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 70%, so the baseline is a 3. The description reinforces the meaning of animateMs (auto-animate 0→1 over the duration) and orientToPath (rotate to face the tangent), which is useful confirmation but largely mirrors the schema text. It adds no meaning for perpendicularOffset, rotationOffset, timelineId, or the concurrency/session parameters (requestId, sessionId, expectedRevision).

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 gives a concrete verb and resource ('Make a layer travel along a path layer') and names the underlying primitive (followPath), so an agent can immediately tell this is a motion-binding operation rather than a geometry edit like add_path or trim_path. It falls short of 5 only because it never explicitly contrasts itself with nearby siblings such as add_modifier or add_binding.

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?

There is no when-to-use or when-not-to-use guidance, no stated precondition that pathLayerId must reference an existing layer of type=path (that fact lives only in the schema), and no named alternative for cases like keyframing position directly. The usage is inferable from the purpose sentence but never stated.

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