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

No annotations are supplied, so the description carries the full burden, and it does explicitly declare the safety profile: read-only, creates nothing. It also discloses the return content (plan limits). It does not say what happens when the key is invalid (error vs. a structured valid=false response), which is the main behavioral gap for a key-check tool.

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 short sentences, front-loaded with the primary purpose and followed by the side-effect guarantee. Nothing is redundant and nothing is missing for its size.

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 zero-parameter diagnostic tool with no output schema, the description covers purpose, side effects, and the shape of the result well enough to call it correctly. The only omission is failure behavior on an invalid key, which would matter for the tool's primary use case.

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 schema has zero parameters and 100% coverage, so the baseline is 4. The description correctly implies the key is derived from context rather than passed as an argument, so no additional parameter explanation is needed.

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 and resource pair: verify the API key works and report its plan limits. This is instantly distinguishable from the watch-management siblings, which all operate on watch objects rather than on the credential itself.

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 makes the use case clear: check credential validity and discover the account's plan limits. There are no overlapping siblings (create/delete/get/list watches) so no exclusions are strictly needed, but it stops short of explicitly saying when to prefer it, e.g. as a pre-flight validation before other calls.

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