set_timeline_duration

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

Annotations already establish that this is a write operation but not destructive. The description adds context that the duration is measured in seconds, must be positive, and that the response is {ok, nodeId}. It doesn't discuss error behavior or side effects, but for a simple setter this is adequate.

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 concise and structured with the primary action first. The second and third sentences respectively give the required prerequisite and return value. No filler or repeated schema text.

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?

Given that the schema and annotations cover the parameter details and safety profile, the description supplies the remaining operational knowledge: how to find timelineId and what response to expect. This is sufficient for an agent to successfully invoke the tool. No output schema exists, but the return format is explicitly stated in the description.

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?

All parameters are fully described in the schema (100% coverage), including units, constraints, and source. The description only restates the duration >0 rule and timelineId provenance, adding little beyond the schema. Thus the baseline of 3 applies.

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 names the target resource ('Figma Motion timeline') and the action ('Set the duration'), with an explicit constraint (must be >0). This directly distinguishes it from other set_* tools that target different properties. It also tells the agent how to obtain the timeline ID, eliminating ambiguity.

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 tells the agent exactly how to get the required timelineId: from get_node_motion via a node's timelines. It also implies the nodeId must reference a node on that timeline. However, it doesn't explicitly state alternatives or scenarios where a different tool would be better, so it's clear but not exhaustive.

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