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

Annotations already state readOnlyHint, openWorldHint, and idempotentHint. The description adds useful behavioral context beyond that: the source records no recurring-versus-guest distinction and the implication for interpreting absence, which is a non-obvious limitation an agent needs to know.

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?

The description is exactly two sentences, front-loading the core operation in the first sentence and then adding the crucial open-world caveat in the second. Every clause earns its place with no redundancy.

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?

Given the rich schema descriptions, output schema, and annotations, the description still fills the remaining semantic gap by explaining the show-versus-episode distinction and why checking the episode guest cast for possible appearances. Nothing the agent needs to call this correctly is missing.

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 100%, so the schema already documents every parameter, including include_crew and its default and the sources for show_id and episode_id. The description adds only the 'optionally with crew' notion, lightly reinforcing the schema but not going beyond the schema's already-rich parameter text.

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 opens with a specific verb and resource: 'List the credited cast of a show with the characters they play' and explicitly distinguishes the show-level and episode-scope modes. This clearly separates it from sibling tools like tvmaze_get_episodes and tvmaze_get_show, whose purposes are different resources.

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 is clear about when to use episode guest cast versus show cast, including the caveat that absence from the show cast list does not prove non-appearance and pointing the agent to 'check an episode’s guest cast for that.' It does not explicitly name sibling tools, but the tool itself already covers the cast-retrieval niche.

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