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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real behavioral meaning beyond that: alignment is order-preserving and insertions/deletions remain explicit rather than being force-matched, which shapes how results should be read. It stops short of describing output shape or limits, but the output schema covers returns.

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 tight sentences with no filler, and the core operation is front-loaded before the alignment caveat. 'Order-preserving narrative-role alignment' is dense jargon but is a genuine specification rather than padding.

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?

The output schema means return values needn't be explained, and annotations cover safety. However, for a two-argument tool whose plan object has a dozen optional per-scene fields including reference_scene_id, the description leaves the agent without guidance on what 'reference' means concretely or how to choose among 30+ siblings.

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 0% on a deeply nested plan object with per-scene fields (role, reference_scene_id, duration_ms, etc.), and the description adds no parameter detail at all. Worse, it calls the second input a 'reference' while the schema names it 'video', leaving the mapping between the prose and the actual argument ambiguous.

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 (compare) and both resources (a plan, one chosen reference), plus the alignment mechanism. The phrase 'one chosen reference' implicitly separates it from the plural comparison offered by compare_groups, though that sibling is never named.

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 implies when this is appropriate ('one chosen reference'), which hints at a contrast with compare_groups, but it never states that contrast explicitly or gives any when-not guidance. The agent must infer the routing decision from the sibling list.

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