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

With no annotations, the description carries the full burden. It implies a read-only operation but does not explicitly state side effects, error behavior for invalid timezone names, or return format. Minimal transparency, though the read-only nature is reasonably inferable.

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 concise sentence that front-loads the resource and operation. It contains no filler or redundancy.

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?

The tool is simple, but the definition is incomplete because the schema does not contain a timezone parameter, and the description does not map the concept to any schema field. No output schema or alternative routing information is provided, so an agent cannot successfully invoke the tool.

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 description mentions a 'named IANA timezone,' but none of the seven input schema parameters (ref, url, city, feed, host, json, path) represent a timezone. Their descriptions, like 'Git ref name; discarded after the shape check,' are unrelated to the tool's purpose. Even though schema coverage is 100%, the parameter descriptions fail to connect to the described functionality, making it impossible to know which parameter to set.

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 'Current time in a named IANA timezone' clearly states the operation (get current time) and the resource (IANA timezone). It implicitly distinguishes from siblings like utc-time and iana-zones by specifying a named zone rather than UTC or a zone list.

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?

No guidance on when to use this tool versus alternatives such as utc-time or iana-zones. There are no explicit exclusions or context clues beyond the basic purpose, leaving the agent to infer usage without support.

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