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

No annotations are provided, so the description carries the full behavioral burden. It does usefully disclose cost ($0.003 per call) and the deterministic output contents, but says nothing about pure-function semantics, permission needs, or limits. Disclosing the price is real added value beyond the schema, hence a 3 rather than lower.

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 compact sentences: what it returns, when to use it, and the cost, with the output description front-loaded. Zero filler.

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?

No output schema exists, but the description enumerates the returned fields (date, weekday, UTC and Tehran times, Unix timestamp), so an agent knows what comes back. The timezone parameter's meaning is also spelled out, leaving little missing for this simple two-parameter read 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?

Schema description coverage is 100%, so both 'at' (ISO-8601) and the 'timezone' enum are already documented in the schema; the description's mention of UTC vs Tehran merely echoes the enum. Baseline 3 applies since the schema does the heavy lifting.

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 (describe) and resource (an instant) and enumerates exactly what is returned: date, weekday, UTC time, Tehran local time, and Unix timestamp. This clearly separates it from siblings like unix_time and weekday_of, which each return only one facet.

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?

Explicitly gives a triggering condition: 'Use it when a response carries a timestamp and the local date matters.' That is clear context, but it names no alternative (e.g. when unix_time or weekday_of would suffice), so the routing guidance is incomplete rather than absent.

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