days_in_month

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the tool's behavior (defaulting to current month if no date is given), which is useful, but does not cover aspects like error handling, date format requirements, or performance traits. This leaves gaps in transparency for a tool with no structured 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 front-loaded with the core purpose in the first sentence and adds necessary detail in the second, with no wasted words. Both sentences earn their place by clarifying behavior and default usage, making it efficient and well-structured.

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?

Given the tool's low complexity (one optional parameter, no annotations, no output schema), the description is mostly complete for basic usage. However, it lacks details on the return value (e.g., integer output) and potential edge cases (e.g., invalid dates), which would enhance completeness for a tool with no output schema.

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 schema has 0% description coverage for the single parameter 'date', but the description compensates by explaining its optional nature and effect (if provided, uses that month; if not, uses current month). This adds meaningful context beyond the bare schema, though it does not specify the expected date format or validation rules.

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 specific action ('Get the number of days in a month') and the resource involved ('a month'), distinguishing it from sibling tools like 'convert_time' or 'current_time' which handle different time-related operations. It also specifies the behavior when no date is provided, making the purpose 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?

The description provides clear context for when to use the tool (to get days in a month, with or without a date input), but it does not explicitly state when not to use it or name alternatives among siblings like 'get_week_year' for different time calculations. This gives adequate guidance but lacks exclusion details.

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