Current time

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorldHint=false, so the safety profile is covered. The description adds value beyond that by clarifying that the time is the server's machine clock in UTC (not the caller's local time) and that a caller-supplied timezone only adds a local rendering – a meaningful, non-obvious semantic.

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?

Purpose is front-loaded in one sentence, followed by usage rationale, then args and returns in compact list form. The Returns block is largely redundant with the existing output schema, which costs a little length, but the overall structure is clean and skimmable.

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-required-parameter, read-only utility with an output schema present, the description covers purpose, usage motivation, and parameter intent. An agent has everything needed to call it correctly; the duplicated return block is harmless redundancy rather than a gap.

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?

Schema description coverage is 100%, so both parameters are already documented with constraints and defaults. The description restates them (IANA zone example, default 'markdown') without adding syntax, fallback behavior for invalid zones, or offset semantics, so it sits at the baseline.

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 first sentence names a specific verb and resource ('Return the current time of the machine running this server') and scopes it precisely to UTC plus an optional IANA time zone. No sibling tool (identification, history, summarize, risk score, webhook verification) overlaps with this, so differentiation is implicit 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?

It gives concrete when-to-use scenarios tied to sibling concepts: judging whether an identification's observed_at is older than a 5-minute window, or how long ago an account was last seen. It lacks any when-not-to-use or named alternative, but no plausible alternative exists among the siblings, so the guidance is nearly complete.

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