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

Annotations already declare readOnlyHint=true, and the description reinforces that with 'nothing is changed' while adding genuinely new context: the call is free and the response shape matches what the editor displays. It stops short of 5 because it says nothing about suggestion count, latency, or failure modes for scenes without a line.

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?

Front-loads the two facts that matter most (free, non-mutating) and then uses compact Args/Returns blocks that are easy to scan. Minor waste remains in redundant lines like 'project_id: project.' and 'scene_uid: the scene.' which merely restate the key names.

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?

There is no output schema, but the description supplies the return shape ({ok, suggestions}), and it covers cost, side-effect profile, and the follow-up tool. What remains uncovered is edge-case behavior — empty scenes, whether suggestions are capped, or how errors surface — which is minor for a read-only helper.

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 only 25%, so the description must compensate, and it does: it explains the conditional requirement that instruction is mandatory for the 'custom' action (a constraint JSON Schema cannot express), confirms the 300-character cap, and enumerates the action modes in readable form. This adds real meaning beyond the raw 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?

States a specific verb and resource: it produces suggestions for ONE scene's line and explicitly notes nothing is changed. It also separates itself from studio_patch by naming that tool as the place where a pick is actually applied, so an agent can distinguish suggestion from mutation without opening either schema.

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?

Gives clear context for use (pick an action style, optionally supply custom instruction) and explicitly routes the follow-up action to studio_patch (set_line). It does not state any when-not-to-use conditions, such as what to do if the scene has no line yet, which keeps it just short of a 5.

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