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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds genuinely useful context the annotations don't cover — that prices are integer micro-USD and quoted per image, per second of video, or per audio clip. It says nothing about pagination, result size, or whether modality filtering is applied, so it adds value but stops short of rich behavioral disclosure.

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?

One dense sentence with zero filler; the resource and the return-value semantics are both front-loaded. Nothing could be cut without losing information.

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 single-optional-parameter, read-only listing tool with no output schema, the description covers the essentials: what is listed and the shape of the returned pricing data. Only the behavior when modality is omitted and any result-size limits are unstated.

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% for the single modality parameter, so the description must compensate. It does name the three modality values (image, video, audio) matching the enum, clarifying that modality selects a model category, but it never states whether omitting it returns all models — a meaningful gap at 0% 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?

States a specific verb (List) and resource (media generation models) plus the scope of modalities covered and the data returned (integer micro-USD prices with per-unit basis). An agent immediately knows this is a model/pricing catalog call and can distinguish it from siblings like generation_quote or create_reel.

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 only implied: the description's emphasis on prices and model modalities suggests it is the discovery step before generation or quoting, but it never states when to call it versus generation_quote or wallet_balance, and gives no exclusions or prerequisites.

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