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

With no annotations, the description carries the full burden of behavioral disclosure. It states the tool returns current time but does not explain whether it includes DST adjustments, timezone offset, or format of the response. It also does not clarify why unrelated parameters like url, host, and json are present, which could confuse an agent about the tool's actual behavior.

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 extremely concise—a single sentence—which is structurally clean. However, it is under-specified: it omits critical details about parameters and output, making it more under-specification than appropriate conciseness. The brevity is not harmful in itself, but it sacrifices necessary context.

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 tool with 4 parameters, no output schema, and no annotations, the description is incomplete. It does not specify the output format (e.g., ISO string, epoch), any error handling, or why unrelated parameters exist. An agent would struggle to call this tool correctly without additional inference. The description falls short of what is needed for safe and accurate use.

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?

Although the schema describes all four parameters (100% coverage), the tool description only implies the 'zone' parameter via 'named IANA timezone'. It does not explain the purpose of url, host, or json, leaving ambiguity about whether they are optional, ignored, or have side effects. The description adds no value beyond the schema and fails to clarify the parameter set's coherence.

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 the tool provides the current time for a named IANA timezone. It distinguishes itself from siblings like 'iana-zones' (which lists zones) and 'utc-time' (which is a specific zone), though it doesn't explicitly name them. The verb 'Current time' and resource 'named IANA timezone' are specific, making the primary purpose clear.

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?

There is no guidance on when to use this tool versus alternatives. The description does not mention when to prefer this over 'utc-time' or 'iana-zones', nor does it explain the role of the other schema properties (url, host, json). It provides no context for selection among siblings.

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