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

Annotations already declare idempotentHint=true, readOnlyHint=false, and destructiveHint=false. The description adds that the overlay is 'editable' and placed at an exact time/layer, but does not discuss retry semantics, expectedRevision behavior, or effects of defaults. Adds some context beyond annotations but not deeply.

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, focused sentence with no wasted words. It front-loads the core action and object, then adds placement details, achieving high clarity in minimal space.

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 8 parameters and an output schema, the description is serviceable but sparse. It does not mention required idempotencyKey, default duration of 4 seconds, or revision handling. It is adequate for basic selection but not fully complete for correct invocation without deeper schema inspection.

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 only 38%, so the description should compensate for undocumented parameters. It only hints at startSeconds and layerIndex via 'exact time and layer' and implies text content, but says nothing about durationSeconds, name, expectedRevision, or idempotencyKey semantics. This leaves most parameters underexplained.

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 clearly states a specific verb ('Add') and resource ('editable text overlay') with precise placement ('at an exact time and layer'). This distinguishes it from sibling tools like add_transition or timeline_media_add, which handle different timeline additions.

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 clear context: it is for adding an editable text overlay to a project timeline. It does not explicitly enumerate exclusions or alternatives, but the specificity makes the intended use obvious relative to siblings. Lacks explicit 'when not to use' guidance.

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