add_caption

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

With no annotations, the description carries the full behavioral burden for a mutation tool. It does not say whether the target track must exist, how overlapping or out-of-order time ranges are handled, whether the change is undoable, or what the response contains.

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?

A single efficient sentence with no filler and the action front-loaded. However, that brevity is achieved by omitting useful context rather than by tight writing.

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 4-parameter mutation tool with no annotations and no output schema, the description is too thin. It omits prerequisites (existing caption track), timing/ordering constraints, and any behavioral notes an agent would need to call it safely.

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 all four parameters (startTime, endTime, text, trackIndex) are already documented in the schema including units and the default track index. The description adds no meaning beyond those field-level descriptions, making the baseline 3 appropriate.

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 uses a specific verb+resource pair ('Add a caption/subtitle segment to a caption track'), which clearly separates it from siblings like update_caption, remove_caption, and add_caption_track. It just stops short of explicitly naming how it differs from those siblings.

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?

There is no statement of when to use this versus update_caption or add_caption_track, and no prerequisites are given. An agent must infer that a caption track must already exist before a segment can be added.

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