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

With no annotations the description carries the full load and does so well: monitoring cadence (~30 min), Ed25519-signed alerts to buyer webhooks on state change, registration cost (0.002 USDC on Base mainnet, up to 24h), and the no-watch fallback. It omits rate limits and any explicit statement of the read-only nature, but the behavioral picture is rich.

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 free status and its return shape before the paid-registration aside, which is relevant because of the registration-pointer fallback. The single sentence is dense and crammed with clauses, but each element carries signal; it is slightly overstuffed rather than wasteful.

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?

With no output schema and no annotations, the description supplies the return fields, the monitoring behavior, and the fallback, so an agent can call and interpret it correctly. Only minor gaps remain (exact pagination/rate behavior, explicit read-only framing).

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 100%, so the single 'url' parameter is already fully documented; the description only restates 'on the given URL' without adding syntax or format detail. The callback mention belongs to the separate registration endpoint, not this tool's parameter, which adds mild rather than clarifying value. Baseline 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?

States a specific resource and scope: 'latest state of any ACTIVE continuous-monitoring watch on the given URL', with the concrete return shape (verdict up/degraded/down, last check, checks count, expiry). This is clearly distinguishable from siblings like world_knock, world_sentinel, and world_status.

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?

Explains the use context (look up an active watch on a URL) and the fallback behavior ('if no watch is active you get a registration pointer'), and points to the registration endpoint for the paid path. It does not explicitly name sibling alternatives to contrast against, so it stops short of a full when/when-not guide.

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