mark_watched

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

The annotations already establish that this is not a read-only operation. The description adds useful behavioral context by explicitly calling out the PLEX_ENABLE_MUTATIVE_OPS requirement, which is key environmental information beyond the basic mutation flag. It does not contradict any annotations.

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 a single efficient sentence that communicates the operation and the crucial prerequisite in very few words. The information is front-loaded and there is no unnecessary filler.

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 simple one-parameter tool with clear annotations and a complete input schema, the description is sufficient to explain the key action and the required environment flag. It could be more complete about expected return behavior or idempotency, but those are less critical given the tool's low complexity.

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 only parameter is fully documented in the schema (ratingKey is described as 'The local Plex rating key of the media item'). Since schema description coverage is 100%, the tool description need not repeat or enrich this parameter. The baseline score of 3 is appropriate.

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 specifies a clear verb 'Mark' with a clear resource 'Plex media item' and the target state 'watched'. Although it does not name alternatives, its wording meaningfully differentiates it from the sibling mark_unwatched and other media operations.

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 includes a configuration prerequisite (PLEX_ENABLE_MUTATIVE_OPS=true) but provides no guidance on when this tool should be preferred over related tools like mark_unwatched, rate_media, or update_metadata. The intended selection criteria are largely left to the agent's inference.

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