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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds two useful behavioural facts — that the call is free and that status has two discrete values, watching or cancelled — but says nothing about ordering, pagination, or volume of results, which an output schema alone may not make obvious.

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?

Three tight sentences, front-loaded with the resource and status, then the sibling routing. The lone filler is "Free.", though it does carry cost information not present elsewhere.

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?

A read-only, one-parameter list tool with an output schema and full annotations needs little prose. The description supplies the status vocabulary and the create/cancel routing, which is everything an agent needs to call it correctly.

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?

There is a single parameter with 100% schema description coverage, including the note that the wallet is "the one that paid" and that results are scoped to it. The description reinforces wallet scoping via "your standing" but adds no new meaning beyond the schema, so the baseline 3 applies.

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?

Uses a specific verb+resource combo — "List your standing URL watches" — and immediately qualifies the scope ("created by check_url_changes") and payload ("each watch's status"). That is enough to separate it from watch_cancel and check_url_changes without opening any schema.

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?

Explicitly routes the two adjacent actions: create via check_url_changes, cancel via watch_cancel. An agent that wants to mutate watches is pushed to the correct sibling, leaving this tool's role unambiguous.

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