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

Annotations already declare readOnly, idempotent, and non-destructive, so the trailing 'Read-only' is largely redundant. The description nevertheless adds genuine behavioral value beyond the annotations: prices track a live model price table (freshness/reliability) and returns are denominated in both USD and credits.

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?

Three tight sentences, front-loaded with what is returned, then usage guidance, then the safety note. The only wasted clause is the final 'Read-only', which duplicates readOnlyHint.

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 and no parameters, the description carries the return-value burden and does so by enumerating the price categories the agent will receive. Enough is stated to call the tool and interpret the result without surprises.

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?

The tool takes no parameters (empty object, additionalProperties false), so there is no parameter syntax to explain and the baseline is a 4. Nothing in the description misleads about inputs.

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+resource ('Current Cast prices in USD and credits') and then enumerates the exact price categories covered: free first video, credit packs, Premium, per-length video costs, and character creation. Siblings (create_video_link, get_showcase, list_characters) are unrelated in scope, so there is no overlap to disambiguate.

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?

Explicitly tells the agent to 'call this instead of quoting from memory', which is actionable when-to-use guidance tied to a real failure mode. It doesn't mention any tool-level alternative, but no sibling covers pricing, so there is little to exclude.

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