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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the operation 'costs nothing' and leaves music and dialogue untouched. However, it does not say whether an existing sfx track is replaced or appended, what happens if it is run twice, or what the call returns — meaningful gaps for a mutation.

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?

Four short sentences, front-loaded with the action, followed by scope, cost and next step — no filler. Minor deduction because 'in sequence length' is grammatically unclear and could be read as a constraint on the clips rather than the track.

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 one-parameter mutation with no output schema, the description covers cost, preserved material and the downstream step, which is a reasonable amount. It falls short on outcome semantics — whether the sfx track is overwritten, appended, or trimmed to the sequence — which an agent needs to call this safely in a repeated workflow.

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?

There is a single required parameter with 100% schema description coverage, and the schema already explains that seq_id is a positive integer as a string. The description never mentions seq_id or adds format or constraint detail beyond the schema. Baseline 3 applies because the schema carries the parameter burden.

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 names a specific verb and resource: laying the clips' own audio as an sfx track for the sequence. It also scopes the operation by saying music and dialogue stay unchanged, which helps separate it from sibling audio tools like lab_sfx, lab_bind_audio and lab_mix. The phrase 'in sequence length' is awkward and leaves the exact placement semantics slightly unclear, but the core action is identifiable.

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?

It gives a clear precondition-free context and an explicit follow-up: 'Then call lab_mix_render', which tells the agent this is a step in a pipeline rather than a terminal action. It also states what the tool will not affect (music, dialogue), which implicitly scopes when it is appropriate. What is missing is an explicit when-not or a named alternative for cases where the agent does want to alter music or dialogue.

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