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

Annotations already mark the tool read-only and non-destructive. The description goes further by disclosing it runs 6 internal checks, reports a pass count, does not probe individual tools, requires no key, costs nothing, has ~200ms latency, and has a rate-limit consideration. No contradiction with 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 well-structured and front-loaded: purpose comes first, followed by an example, when-to-use/not-to-use rules, cost, and latency. Every section earns its place and contributes to an agent's operational decision-making.

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 no-parameter, read-only health check, the description is complete: it states scope, exclusions, usage timing, rate limits, authentication requirements, cost, latency, and expected outcome ('reports how many passed'). No output schema exists, but the description gives enough for an agent to interpret the result.

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 and 100% schema coverage, so the schema fully defines the calling contract. The description reinforces this with an example call of self_test({}) and adds no unnecessary parameter details, which is appropriate for a no-parameter 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?

The description clearly states a specific action and resource: a 'Service health probe' that 'runs 6 internal checks and reports how many passed.' It explicitly says it does NOT probe each tool individually, which differentiates it from status/verification siblings and removes ambiguity about its scope.

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 explicit WHEN TO USE guidance: at agent startup, before high-stakes task sequences, and after unexpected errors. It also gives a WHEN NOT TO USE rule (do not call more than once per minute in production) and clarifies that per-tool probing is out of scope.

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