now-time-info

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

Annotations already cover the safety profile (readOnlyHint=true), and the description still adds genuinely useful context: ISO output format, deterministic no-parameter behavior, and the important disclosure that the data is fictional demo data not connected to official McDonald's services. '只读，无参数' partially restates the annotations, which is the only redundancy.

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?

Three short sentences, all front-loaded, with the essential fact (what it returns) first and the demo-data caveat last. The clause '只读，无参数' duplicates structured data and is the one sentence fragment that doesn't fully earn 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?

For a zero-parameter read-only utility with no output schema, the description covers everything: return format, intended use, safety, and data provenance. An agent has all it needs to call it correctly.

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?

Zero parameters, so the baseline is 4; the description explicitly confirms '无参数', removing any doubt about how to invoke it. Nothing further is needed for an empty schema.

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?

States a specific verb and resource ('返回当前日期和时间') plus the exact return format (ISO 格式), which clearly separates it from the query-oriented siblings. It stops short of explicitly naming which sibling to pair it with, but the utility nature is unambiguous.

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?

Gives concrete use contexts — judging store business hours and coupon validity — which tells the agent when this tool is the right one to call. It does not state exclusions or name a specific alternative, so it falls short of a full when/when-not routing statement.

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