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

There are no annotations, so the description must carry the burden of behavioral disclosure, but it says nothing about side effects, return format, or whether the tool is a read-only lookup. The only behavioral hints, such as 'discarded after the shape check,' appear in the parameter schema rather than the description itself.

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 concise and contains no filler, but it is a noun phrase rather than a complete statement and is under-specified for a tool with nine parameters. Brevity is present, but the structure does not efficiently convey the tool's operation.

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?

With nine optional parameters, no annotations, and no output schema, a one-sentence description is severely incomplete. The description does not explain what the tool returns, how to request zones, or how the 'discarded after' parameters affect invocation, so an agent cannot reliably decide whether or how to call it.

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 the baseline is 3. The main description adds no parameter-level meaning and does not clarify which of the nine optional parameters actually influences the result, such as 'zone' versus the others described as discarded. It therefore stays at baseline rather than adding value.

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 is a noun phrase ('Common IANA timezone names for clock calls') that largely restates the tool name ('iana-zones') rather than stating an action like returns, lists, or validates. It adds 'common' and 'clock calls' as context, but an agent still cannot tell whether the tool returns a list of zones, validates a zone, or resolves aliases.

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 gives no explicit guidance on when to use this tool versus siblings like timezone, utc-time, or calc-eval. The phrase 'for clock calls' hints at a use case, but there are no conditions, exclusions, or alternative tool references.

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