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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds real value: it discloses that output is 2-3 contrasting variants, that timing scaling is explicitly a proposal rather than a fact, and that under-sampled patterns will not be passed off as norms. Those are non-obvious output-epistemics that annotations cannot convey.

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 zero filler, and the output contract is front-loaded before the caveat. It is arguably too terse for the parameter surface it must cover, but no sentence is wasted.

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?

An output schema exists so return values needn't be explained, and annotations cover the safety profile. Still, for a 6-parameter, nested-object tool in a crowded sibling set, the description leaves the filtering/cohort controls and the sibling boundary undefined, which is a real gap for correct invocation.

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% across 6 parameters, including a nested filters object with nine sub-properties, so the description must carry the load. It only maps 'two or three' to variants and 'exact-duration' to duration_ms, saying nothing about aspect, min_videos, allow_broaden, or any filter field, leaving most of the surface undocumented.

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?

Names a specific verb and artifact ('Create two or three contrasting exact-duration plans') sourced from 'cited observed sequences', which tells an agent what comes out. It does not, however, distinguish itself from near-siblings like typical_structure, critique_plan, or reference_brief, so an agent must guess at the boundary.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative even though typical_structure and critique_plan sit right next to it. The second sentence is a behavioral caveat about proposals and under-sampling, not usage routing.

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