play_timeline

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

Annotations establish it is a non-destructive, idempotent, non-open-world action, but the description adds real context beyond them: it returns immediately, mutates no asset, keeps playing if already playing, reports 'playing' right after the call, and errors when the sequence is missing or unroutable. The stated 'keeps playing' behavior is consistent with idempotentHint=true, not a contradiction.

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-loaded with the action, followed by routing, side-effect, and error clauses; every sentence carries information. It is dense and heavily semicolon-claused, which costs a little readability, but nothing is filler.

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?

With no output schema, the description supplies the return shape ({ sequence_name, playing }), the error conditions, the side-effect profile, and the sibling workflow. Nothing an agent needs to call it correctly is missing.

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 100% so the schema already defines sequence_name, but the description adds lookup semantics the schema lacks: the name is resolved as an asset name scoped under /Game and is opened in the Sequencer if not currently shown. That is meaningful meaning beyond the field description.

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 (starts playback), the exact subsystem (editor's Sequencer), and the resource (Level Sequence found by asset name under /Game), plus the implicit open-first behavior. It is instantly distinguishable from play_level_sequence_runtime, which it names.

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?

Explicitly gates the tool ('Editor preview only, no PIE or game player') and routes the agent to the alternative (play_level_sequence_runtime) for that case. It also names the follow-up siblings pause_timeline and set_timeline_time, so the agent knows the surrounding workflow.

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