Verify credentials and upstream reachability

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

Even though annotations already mark readOnlyHint, idempotentHint, and openWorldHint, the description adds valuable behavioral details: it reports the credential source, acceptance status, round-trip time, and a plain-English failure-mode hint. It also explicitly promises 'never returns the credential itself,' which is important safety context beyond the annotations.

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 description is moderately long but every sentence earns its place: mechanism, outputs, usage trigger, and safety guarantee. It is front-loaded with the core behavior and avoids filler, though the final sentence could be viewed as slightly repetitive with 'Read-only'.

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 is complete: it explains what the tool does, what it returns (source, acceptance, RTT, hint), when to use it, and a key safety property. An agent has all the information needed to invoke and interpret the call.

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 input schema has zero parameters, so there is nothing to document. The description explains that the tool resolves credentials internally, which is sufficient. The 0-parameter baseline of 4 applies here.

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 description names a specific action ('Resolves the credential... makes one authenticated request to api.freshbooks.com') and a clear diagnostic resource. It is unmistakably distinct from sibling CRUD/auth tools because it focuses on credential validation and upstream reachability, not on Fetching or mutating data.

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 explicitly states when to use the tool: 'Call this when a real tool fails and you want to know which hop broke.' This provides clear contextual guidance, though it does not explicitly list exclusions or sibling alternatives. The trigger condition is precise enough for an agent to select it over other tools.

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