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

Adds substantial behavior beyond annotations: per-check billing at the endpoint's own credit cost, refunds on failure or empty result, and that creating a watch is free. Annotations (readOnlyHint=false, destructiveHint=false, openWorld=false→openWorld=true) cover safety but not the cost/refund model, which is the key operational trait here.

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?

Two sentences, zero waste, with the core action and the cost implication front-loaded. Every clause earns its place.

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 4-param scheduled-watch tool with no output schema, the description plus rich schema give an agent everything needed to invoke it, and the cost model fills a real gap. Minor omission of what the webhook POST payload looks like could matter but is secondary.

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% and the deletion-sensitive details (endpoint restrictions, interval bounds and defaulting behavior) are already documented in the schema, so the description only needs to point at webhook_url delivery which it does. 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?

States a specific verb chain (check on a schedule, POST to webhook_url when data changes) against a specific resource (endpoint), so it is instantly distinguishable from companion tools like list_watches and cancel_watch and from direct endpoint calls.

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 implies usage (polls on a schedule, notifies via webhook) but offers no explicit when-to-use vs. a direct one-off endpoint call, nor any exclusion of the non-watchable search/trending endpoints at the description level (that constraint lives in the endpoint schema).

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