date_infoCalendar facts about a date (UTC): weekday, day-of-year, ISO week number, quarter, whether the year is a leap year, and days in that month.
| Name | Required | Description | Default |
|---|---|---|---|
| date | Yes | A date (ISO-8601). |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "date": "2025-12-25"
+ },
+ {
+ "date": "2024-02-29T14:30:00Z"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint, idempotentHint, and destructiveHint, so the tool is clearly safe and idempotent. The description adds the UTC context but does not disclose behavior for invalid dates or time portion handling. The description adds some value beyond annotations.
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, well-structured sentence that efficiently conveys the tool's purpose and outputs without redundancy or unnecessary words.
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 simple tool with one parameter and no output schema, the description is fairly complete. It lists all expected outputs. A minor gap is not specifying the return format (e.g., JSON object), but overall it is adequate.
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 for the single parameter is minimal ('A date (ISO-8601).'), but the description enriches it by listing the specific calendar facts computed from the input, giving the agent a clear idea of what the parameter affects.
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 states the tool returns calendar facts about a date in UTC, listing specific outputs like weekday, day-of-year, ISO week number, quarter, leap year, and days in month. This clearly distinguishes it from siblings like date_diff (difference between dates) and add_duration (add/subtract duration).
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 implies use when calendar facts are needed, and siblings provide clear alternatives (date_diff for differences, add_duration for arithmetic). However, it does not explicitly state when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.