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

Annotations declare readOnly, idempotent, non-destructive, closed-world, and the description corroborates this by stating it "opens nothing by itself" and only returns instructions — an important clarification that keeps the agent from assuming a side effect occurred. It still doesn't say what the returned steps look like or how they vary by Plex client.

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 core workflow is front-loaded and short, but the trailing note about Plex's official HTTP API and "checked 5 Nov 2026" adds no actionable information for selecting or invoking the tool. Two of the four sentences pull their weight; the rest is padding.

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 no-parameter, no-output-schema tool the description covers the call-then-browse pattern adequately, but it leaves open how the item is chosen and whether the returned guidance differs by Plex client (web, mobile, TV). Those gaps matter for correct downstream execution.

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 schema has zero parameters, which normally sets a baseline of 4, but the description never explains how the target item is identified (presumably from the current Plex Cloud Browser session). That omission is meaningful for a tool whose whole job is to describe marking a specific item watched.

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 name and title say "Mark item watched in Plex," but the description reveals the tool actually returns step-by-step instructions and "opens nothing by itself." That correction is valuable, yet the opening sentence ("Mark item watched in the user's own Plex account") still reads as if the tool performs the action, leaving the true purpose ambiguous until the second clause.

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 a clear workflow: call this to get the procedure, then execute it with cotlet_browser_* tools in the user's Plex Cloud Browser. It does not name or exclude sibling Plex tools (plex_add_to_watchlist, plex_list_library_items), so an agent gets context but no explicit when-not guidance.

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