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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds valuable context beyond those: the exact number of checks, the fact that it does not probe individual tools, cost, latency, and a rate-limit warning. No contradictions 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 with front-loaded purpose, followed by example, usage guidance, cost, and latency. Every section adds decision-relevant information with no redundancy.

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 health probe with strong annotations, the description is complete: it explains what is checked, what the result means, when to call it, when not to call it, and operational characteristics. No output schema exists, but 'reports how many passed' is adequate for this simple tool.

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 the schema imposes no semantic burden. The description reinforces the empty call with 'call self_test({})' in the example, which is sufficient; no deeper parameter explanation is needed.

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 a specific verb and resource ('Service health probe: runs 6 internal checks and reports how many passed') and explicitly distinguishes this from checking individual tools. It clearly says what the tool does and what it does not do.

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?

Explicit 'WHEN TO USE' guidance covers startup, high-stakes sequences, and error recovery. 'WHEN NOT TO USE' gives a concrete rate-limit constraint, and the 'does NOT probe each tool individually' statement helps route agents away from incorrect use.

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