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

Well beyond annotations: it discloses the daily comparison cycle, the page cap (10), the three outcome categories (break/drift/note) with concrete triggers for each, that no scan credit is consumed, and quota ceilings per plan. This is consistent with readOnlyHint=false (it creates a watch) and destructiveHint=false (nothing is removed).

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?

Front-loads the action, then explains mechanism, outcomes, and cost in a single dense sentence. The nested parentheticals (page definition and break triggers) are load-bearing but make the sentence harder to parse than necessary; splitting outcome definitions into their own sentence would help.

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?

Covers what an agent needs to decide and call: prerequisites (an existing scan), cost, limits, and what the watch does. With no output schema, it does not indicate what comes back (watch identifier, confirmation) or whether calling twice creates a duplicate watch — the main residual gap.

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 coverage is 0% and the single scan_id parameter has no description in the schema. The description partially compensates by tying the parameter to 'one of your scans', but it never says where to obtain a scan_id (e.g., from list_scans) or what happens if the scan is stale.

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?

Specific verb + resource: 'Start watching the site of one of your scans.' The description also explains the mechanism (daily re-read of the scanned pages plus product pages, up to 10), which clearly separates it from one-off tools like recheck_page and from get_watches, which only lists existing watches.

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?

Gives a clear context for use (after a scan, to keep monitoring that site) plus cost/quota guidance: free, no scan consumed, and plan-based limits (Free 1, Pro 1, Growth/Lifetime 5). It does not explicitly say when to prefer this over recheck_page, so it stops short of full when/when-not routing.

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