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

The annotations already declare a non-read-only, open-world, non-idempotent, non-destructive create operation. The description adds substantial behavioral context beyond that: polling every interval_sec (default 300), down/recovery alerts, guest_token secrecy, billing/402 handling, schedule ownership, missed-run detection, and alert timing tied to the check cycle. Some sentences are tangential, but the behavioral disclosure is strong.

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 first sentence front-loads the core monitoring behavior, but the description then strings together several operational notes without tight grouping. The sentence about a check-in proving the signal arrived rather than a backup being restorable is tangential to create_site, and a few other notes could be consolidated or removed.

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 moderately complex create tool with a nested check object, no output schema, and rich schema coverage, the description covers setup behavior, guest_token output, billing, and alert scheduling. However, it omits the normal success return shape, such as a site identifier or monitor details, and does not explicitly guide the agent toward or away from sibling tools.

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 description coverage is 100%, so all 8 parameters, including the nested check object fields, are already documented in the schema. The description reinforces interval_sec default 300 and guest_token ownership but does not add meaningful semantics for name, tags, alert_to, alert_url, or paused_until beyond what the schema already provides, making the baseline 3 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 opening sentence identifies the resource and action clearly: it sets up a website monitor that calls check.url at an interval and alerts on downtime and recovery. It is understandable as a creation/setup tool, though it does not explicitly name or distinguish itself from siblings such as check_site or list_sites.

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 supplies some usage prerequisites, including reading billing before a paid option, the 402 charged-request behavior, and guest_token handling when no owner token is supplied. It also hints that a single paid probe is not continuous monitoring, but it never explicitly names check_site or states when not to use create_site, so the boundary with alternatives is left to inference.

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