marker_add_sustain_point

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

Without annotations, the description carries the burden of explaining behavior. It clearly states that the playback holds until a keyoff command releases it, which is the key behavioral trait. However, it does not mention potential side effects or error conditions (e.g., invalid track_target), leaving a minor gap.

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 succinct, using two short paragraphs and an example. No redundant or verbose wording is present, and the structure is clear and direct.

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 simple two-parameter tool, the description covers purpose, usage, and parameters adequately. It does not mention output schema (which is absent) or prerequisites, but the tool's simplicity means these omissions are not critical. The example and reference to keyoff provide sufficient context for typical use.

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?

Both parameters are well-described: track_target is identified as a GUID from event_add_marker_track, and position is given as 'Timeline position in seconds (>= 0)'. The description adds meaningful context beyond the plain schema properties, which only provide titles.

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 explicitly states the action ('Add a sustain point') and explains its function: playback holds at the point until a keyoff event releases it. It also differentiates this from other marker actions like 'add_region' or 'add_transition' by specifying the sustain behavior.

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?

The description provides usage context ('Used for loop-until-released sounds') and a concrete example ('a footstep that holds mid-loop until the game says "stop"'). It implies when to use this tool vs. alternatives, though it does not explicitly compare with other marker tools.

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