List the languages the catalogue holds

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

Annotations already say readOnlyHint, idempotentHint, and destructiveHint=false, and the description adds meaningful behavioral detail: results are measured over one season and counted in episodes, and six site codes differ from ISO 639-1 with one collision ('br' for Brazilian Portuguese vs. Breton). This is exactly the kind of domain quirk an agent needs before filtering subtitles.

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 dense but every sentence carries distinct information: core purpose, default behavior, show-level behavior, output fields, and a critical code-collision warning. It is front-loaded with the main verb and resource, and the warning is placed where it matters before the next tool step.

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 annotations, full schema coverage, and an output schema, the description covers everything an agent needs: both invocation modes, parameter meaning, the data returned per entry, and a domain caveat. It also connects the tool to the surrounding workflow by telling the agent to read this before narrowing list_subtitles.

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 input schema already describes both parameters well, so the baseline is 3. The description adds extra context beyond the schema: the no-argument call returns exactly twenty-four languages, and the show-level result is 'measured over one season and counted in episodes,' which clarifies how id and season behave in practice.

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 first sentence states exactly what the tool does: 'List the languages tvsubtitles.net catalogues subtitles in.' It names the resource (languages) and the site, and the following sentences distinguish the two modes (whole catalogue vs. a specific show), setting it apart from siblings like list_subtitles and search_titles.

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 gives explicit usage guidance: call without arguments for the catalogue-wide list, or pass a show id from search_titles to see what one show holds. It also tells the agent when to use this tool relative to a sibling: 'Read this before narrowing list_subtitles by language.'

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