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

Annotations only declare the safety profile (not read-only, not destructive, closed-world); the description adds real behavior beyond that: lines that overrun the next caption are sped up, the default track selection logic, and that the call consumes the workspace's monthly voice/music minutes. It does not describe the approval flow in prose, but the approvalId parameter covers that.

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?

Two dense sentences with the core action front-loaded and no filler. The quota note is a useful trailing clause rather than padding, though the sentence is packed tightly enough to require a second read.

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 six-parameter mutation tool with no output schema, the description covers purpose, default source, timing behavior, and cost. The main omission is any mention of the approval gate in prose, which is left entirely to the approvalId parameter description.

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 already 83%, so the schema documents most parameters. The description adds the default-source behavior for clipIds and the per-clip timing semantics, but nothing about volume, language detection, or voice selection beyond what the schema states. Baseline 3 is 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?

States a specific verb and resource ('Read caption clips aloud ... on the Voiceover track') plus the mechanism (ElevenLabs) and the timing behavior. An agent can distinguish this from add_voiceover or generate_captions 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?

Gives a clear use case ('for ads carried by captions or on-screen text') and a default source track, which tells the agent when this is the right tool. It stops short of naming the sibling alternatives (add_voiceover, generate_captions) or stating when not to use it.

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