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

Annotations already declare idempotent, non-destructive, non-read-only behavior, and the description adds genuinely new operational context: timelines up to 20 s are checked inline and may wait for a render when the server is busy, while longer ones return a task or job. It also clarifies that only junctions between two clips are examined and that a null word means a clean cut, not a missing reading. It does not discuss cost, permissions, or failure modes, so a 4 rather than 5.

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?

The description is front-loaded with the core measurement purpose and then layers the optional analyses, with no filler sentences. It is dense and long-sentenced, which slightly hurts scannability, but every clause carries information an agent needs.

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 an output schema present, the description need not explain return values, and it correctly focuses on inputs, opt-in behavior, and the sync-vs-async execution model. The main remaining gap is that the 'range' parameter's effect on measurement scope is never described, which matters for a measurement tool.

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 80%, so the schema already documents most parameters, and the description largely restates the opt-in semantics of black/silence/speech rather than adding syntax or format detail. It does add real meaning for the speech block (Silero VAD on the mix, per-clip-edge transcript word, null-word interpretation), but the range and timeline_id parameters get nothing beyond the schema. Baseline 3 is appropriate given the high coverage.

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 opens with a specific verb and resource ('Measure the rendered timeline') and enumerates the exact metrics produced: gaps, offline media, frame count, LUFS, true peak, black and silent stretches, and per-cut speech facts. This is clearly distinguishable from siblings like media.analyze or timeline.diff, which do not measure rendered output.

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 states the conditional activation of each optional analysis ('when you give their settings', 'left out, none are looked for', 'left out, cuts are not listed'), which tells the agent exactly how to opt in. It also explains the short-vs-long timeline execution path. It does not name an alternative tool or say when not to use this one, so it falls short of a 5.

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