now_iso

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

With no annotations provided, the description bears the full burden of behavioral disclosure. It explicitly says the output formats (ISO-8601 UTC, unix seconds) and discloses a key limitation: the IANA timezone label is derived only from the offset, not a full timezone database. This is useful context that goes beyond the schema, though it does not explicitly state the tool has no side effects.

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 a single, front-loaded sentence that states the core purpose and key limitation without any filler. Every word contributes useful information, making it highly concise and well-structured.

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 simple stateless tool with one optional parameter and no output schema, the description fully covers the purpose, return formats, and a crucial limitation. The agent has enough information to invoke it correctly without needing further details.

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 schema already documents offset_minutes with an example, giving 100% coverage. The description adds meaning by linking this offset to the optional IANA timezone label, clarifying that the parameter controls the label output. This enriches the parameter semantics beyond the schema's simple 'local offset' description.

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 that the tool returns the current time in ISO-8601 UTC, unix seconds, and optionally an IANA timezone label. It is the only time-related tool among the siblings, so its purpose is unmistakable, even though it lacks an explicit verb like 'get' or 'fetch'.

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 implies when to use this tool: whenever the current time or timestamp is needed. The parenthetical 'offset only — no full tz DB' provides a caution about its limitations, effectively telling the agent not to use it for full timezone database lookups. However, it does not explicitly name alternative tools.

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