Verify credentials and upstream reachability

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

Annotations cover the safety profile (readOnly, idempotent, openWorld), and the description still adds meaningful behavior: it enumerates what the report contains (credential source, acceptance, round-trip time, plain-English hint) and adds the security-relevant guarantee that the credential itself is never returned. The three-way error taxonomy ('no credential' vs 'rejected' vs 'upstream problem') is exactly the kind of context annotations cannot convey.

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-loaded with what it does and back-loaded with when to call it, which is good ordering. Three sentences is reasonable, though 'www.groupon.com' is repeated three times and could be stated once, making it slightly heavier than necessary.

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 carries the full burden of describing the return value, and it does so precisely (source of credential, acceptance, RTT, hint). No parameters to document and annotations cover safety, so nothing an agent needs before calling is missing.

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?

There are zero parameters, so there is nothing to disambiguate and the baseline is 4. The description correctly avoids inventing parameter behavior for a no-arg tool.

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 concrete verb and resource: it resolves the credential and makes one authenticated request to www.groupon.com, then reports the diagnostic result. This is unmistakably distinct from the sibling tools (cart, deal, search, purchase), which are all user-facing commerce operations.

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?

Gives an explicit trigger: 'Call this when a real tool fails and you want to know which hop broke.' That clearly frames it as a diagnostic path rather than a normal-operation tool. It stops short of naming which sibling to try instead or stating not to call it in the happy path, so not quite a 5.

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