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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), so the bar is lower, and the description adds genuinely useful operational context: the required Bearer credit-token auth on the transport and a docs link. It still omits rate limits and whether the list is paginated or truncated.

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, front-loaded with the core action, then the auth prerequisite and docs link. Nothing is padded or redundant.

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, the description usefully enumerates the returned fields and covers the auth requirement and read-only nature. It stops short of describing ordering, size limits, or what an empty watch list looks like, which an agent consuming the result would want.

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?

The tool takes zero parameters, so the baseline is 4; there is nothing for the description to disambiguate. The enumerated return fields (status, interval, cost per day, last check, last change) describe output rather than inputs, which is a bonus but not a parameter concern.

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+resource ('List the webhook watches of your credit token') and enumerates what each returned watch carries (status, interval, cost per day, last check, last change). The read-only listing intent is unambiguous, though it never explicitly contrasts itself with watch_create/watch_delete siblings.

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?

Usage is implied by the description plus the stated prerequisite ('Needs "Authorization: Bearer <credit token>" on the MCP transport'), which is real guidance. However it never says when-not to use it or points to watch_create/watch_delete as the mutation alternatives in the same family.

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