ctrl_assign_expression

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

The annotations already signal that this is not read-only and is destructive. The description adds a reliability/scope caveat but does not disclose what happens to an existing controller on the property or whether the assignment is a replacement. This is acceptable given the destructiveHint annotation, but some behavioral context is still missing.

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 core action and caveat are front-loaded and the wording is tight. The bilingual repetition is mildly redundant, but the total length is still small and each unique idea is stated clearly.

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 3-parameter mutation tool with complete schema descriptions and annotations, this is mostly complete: it covers the action, target property type, expression usage, and the main alternative. It does not mention whether an existing controller is overwritten or what the return status is, but this is not critical for the core call.

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 description coverage is 100%, so the baseline is 3. The description does not add much parameter-level meaning beyond what the schema already provides: property is described as scalar, and expression already includes an example in the schema.

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 that it attaches an Expression controller to a scalar property and drives it with an expression. It also explicitly contrasts this with transform tracks, which should use a List controller with a Noise layer, so it is distinguishable from nearby controller tools like ctrl_add_list and ctrl_wire.

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 explicit usage guidance: Expression controllers are most reliable on float/scalar properties, and transform tracks should instead use a List controller with a Noise layer. This tells an agent exactly when to use this tool and when to choose an alternative.

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