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 genuinely useful behavioral context beyond that: the '$0' cost disclosure, the null-means-platform-default convention with the fallback listed in `platformDefaults`, and the fact that each format flags whether it requires an explicit spend confirmation.

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?

It is dense but front-loaded: the primary resource and the meaning of the id come first, followed by the secondary catalogues the call also returns. No sentence is filler, though the trailing '$0' and the long enumeration of auxiliary payloads make it heavier than a pure list tool usually 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 no output schema, the description carries the full burden of describing returns and does so thoroughly: the referent fields, the null/platformDefaults convention, the extra catalogues (duration profiles, output formats, budget tiers, writingProfiles, sceneOptions), the effect of both parameters, and the zero cost.

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 100%, so the baseline is 3. The description goes slightly beyond the schema by tying `compact` to this tool's own payload — it names exactly what is dropped (pacing curve, per-format writing measures, writing catalogue) rather than the schema's generic 'heavy, rarely needed parts', and reinforces that `locale` governs the readable strings.

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 the resource precisely — 'the creative referents — the formats a piece can be produced in' — and enumerates the fields each referent carries, which is far more specific than the title 'List formats'. It is clearly separable from siblings like list_cast, list_material or list_versions by content, though it never explicitly contrasts itself with them.

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?

Usage is implied rather than stated: 'The referent id is the value of `creative_referent` when a piece is created or priced' tells the agent how the output feeds other calls, which strongly hints this is a prerequisite lookup. However there is no explicit when-to-use/when-not guidance, no mention of estimate/produce as the downstream consumers, and no exclusions.

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