set_subtitle_cue_timing

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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is partly covered. The description adds genuine behavioral context the annotations lack: the load-modify-save flow on USubtitleAssetUserData and the partial-update guarantee ('Fields not provided are left untouched'). It also spells out the full return shape despite no output schema.

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 purpose, followed by the mechanism and a structured Returns block. The Returns listing is somewhat long but justified because there is no output schema to convey it. Every sentence earns its place; only mild redundancy between the prose and the field list.

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 mutation tool with 5 params, no output schema, and partial-update semantics, the description is nearly complete: it covers the load/apply/save lifecycle, the untouched-field behavior, and the return values. It omits only permission/prerequisite context, which is minor here.

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 schema already documents all five parameters. The description merely restates the three optional fields and their role in the update, adding no format, unit, or constraint detail beyond what the schema ('Optional new Duration (seconds)', etc.) already provides. Baseline 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?

States a specific verb and resource ('Updates the timing fields on an existing subtitle cue') and names the exact fields and array target (Subtitles[cue_index]). This distinguishes it cleanly from sibling tools like set_subtitle_cue_text (text) and add_subtitle_cue (creation). An agent can select it without opening the 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?

The description implies usage by specifying that it applies 'any combination' of the three optional fields and that unprovided fields are untouched, which tells the agent this is a partial-update tool. However, it never names alternatives (e.g., set_subtitle_cue_text) or states explicit when-to-use / when-not conditions.

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