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

With no annotations, the description carries the full burden. It discloses that the tool returns UTC and optionally local timezone based on city, and mentions the purpose of timezone offset. It does not explicitly state read-only behavior, but 'returns' implies it. No side effects or limitations are hidden, making it transparent enough for a simple read-only tool.

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?

Two sentences with zero waste. The primary functionality is front-loaded, followed by a practical usage tip. Every word earns its place.

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 low complexity (one optional parameter, no output schema). The description covers the function and a specific use case, and the schema covers valid cities. While it doesn't specify return format or error handling, these are minor for a simple datetime tool, making it sufficiently complete.

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 coverage is 100%, so the description does not need to document the city parameter. However, it adds meaning by explaining that providing a city yields local time and offset, connecting the parameter to the tool's behavior. This goes beyond the schema's basic definition.

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 verb 'returns' and the resource 'current date and time,' with explicit mention of UTC and optional local timezone. It is unambiguous and easily distinguished from the unrelated sibling tools like create_order or cancel_job.

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 provides an explicit use case: 'Call this before create_order to get the correct timezone offset.' This gives clear context on when to use the tool, though it does not explicitly mention alternatives or exclusions. Since no sibling provides datetime, this is acceptable.

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