Verify credentials and upstream reachability

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

Annotations already declare readOnlyHint and idempotentHint, so the description's 'Read-only' statement adds little beyond that. However, it goes further by disclosing it never returns the credential itself, explains the diagnostic outputs (source, acceptance, round-trip time, plain-English hint), and the nature of the single authenticated request. This adds meaningful behavioral detail beyond the annotations, though it doesn't cover every edge case like rate limits or exact response format. With annotations present, this is solidly above baseline.

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 four sentences long, each adding distinct value: purpose, output details, read-only safety, and usage trigger. It's front-loaded with the core action, and there is no fluff or redundancy. Every sentence earns its place, making it an exemplar of concise, structured writing.

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, no-output-schema health-check tool, the description covers all essential aspects: what it does, what it reports, when to use it, and a safety guarantee. It doesn't leave an agent guessing about the tool's scope or limitations. The description is complete for its purpose, especially given the rich annotations that already convey read-only and idempotent behavior.

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 has zero parameters, so the schema covers everything (100% coverage trivially). The description correctly avoids discussing parameters since none exist. According to the rubric, 0 params gives a baseline of 4, and the description doesn't need to add anything. It appropriately focuses on behavior and output.

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 clearly states the tool's purpose: it resolves the credential and makes an authenticated request to api.signupgenius.com, then reports diagnostics. It names the specific resource and action, and distinguishes itself from sibling tools by indicating it's for diagnosing failures ('Call this when a real tool fails'). This is explicit and unambiguous.

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 gives a clear when-to-use: 'Call this when a real tool fails and you want to know which hop broke.' This is explicit context but doesn't name alternatives or explicitly state when not to use it. However, the condition is clear enough that an agent can infer it's not for normal operations. It stops short of naming sibling tools as alternatives, so it earns a 4 rather than a 5.

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