Verify credentials and upstream reachability

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

Beyond the readOnlyHint=true and idempotentHint=true annotations, the description adds that it never returns the credential, performs exactly one authenticated request, diagnoses three distinct failure categories, and reports credential source and round-trip time. This is rich, honest behavioral disclosure with no contradiction to 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 compact yet information-dense. Every sentence contributes: what the tool does, what it reports, what it never returns, and when to use it. The 'Read-only' safety note is placed early, and the usage trigger closes the description cleanly.

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, read-only diagnostic tool without an output schema, the description fully covers inputs, behavior, safety, output semantics, and the intended failure scenario. Nothing an agent needs to decide when to call it or interpret its result 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, and the schema description coverage is 100% by default. The description correctly focuses on behavior rather than parameters. Baseline 4 applies because there is nothing parameter-related to explain.

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 states the exact action ('resolves the credential', 'makes one authenticated request'), the target upstream, and what it reports. This clearly distinguishes mhlb_healthcheck from sibling tools like mhlb_whoami, which likely checks identity locally rather than upstream reachability.

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 an explicit trigger: 'Call this when a real tool fails and you want to know which hop broke.' It does not enumerate alternatives or when-not-to-use conditions, but the stated use case is specific and actionable.

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