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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description confirms read-only behavior ('Return'). It adds the return format (UTC ISO 8601), which is useful context. No side effects described, but none are implied by the tool's nature. The description is consistent 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?

Extremely concise: one sentence stating the action and format, followed by a short usage hint. Information is front-loaded and every word earns its place. No fluff.

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 tool with an output schema present (has_output_schema: true), the description is fully sufficient. It tells what the tool returns (UTC ISO 8601) and why to use it (aliveness check). Nothing missing for correct invocation.

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?

Tool has zero parameters, so the description need not explain any. The baseline for 0 params is 4, and the description does not add or need parameter details. Schema coverage is 100% (no params).

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?

States a specific verb ('Return') and a precise resource ('server's current time in UTC (ISO 8601)'). Clearly distinct from siblings like add_numbers and get_rule_of_thumb, which have unrelated purposes. No ambiguity.

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?

Explicitly suggests a use case: 'Useful for checking the server is alive.' This gives clear context for when to call the tool. Does not discuss alternatives, but given the tool's simplicity and unrelated siblings, no exclusion is needed.

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