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 adds some context beyond the basic function: it mentions default behavior (year/month default to current) and return info ('first/last day info'), which helps the agent understand output structure. However, it lacks details on error handling (e.g., invalid month values) or performance traits, leaving gaps for a tool with no annotation coverage.

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 well-structured and appropriately sized. It starts with a clear purpose statement, followed by organized sections for 'Args' and 'Returns' with bullet-like formatting. Every sentence earns its place by providing essential information without redundancy, making it easy to parse and understand quickly.

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 (simple date calculation), no annotations, and the presence of an output schema (implied by 'Returns' info), the description is mostly complete. It covers purpose, parameters, and return values adequately. However, it could benefit from mentioning sibling tools for better contextual placement, slightly reducing completeness for agent selection.

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 description adds significant meaning beyond the input schema, which has 0% description coverage. It clearly explains both parameters: 'year' (with example '2025' and default to current year) and 'month' (with range '1-12' and default to current month). This fully compensates for the schema's lack of descriptions, providing all necessary semantic context for parameter usage.

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 tool's purpose: 'Get the number of days in a month.' This is a specific verb ('Get') + resource ('number of days in a month'), making the function immediately understandable. However, it doesn't explicitly differentiate from sibling tools like 'get_datetime' or 'get_week_year', which might also provide date-related information but with different focuses.

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 no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools like 'get_datetime' (which might provide date info) or 'relative_time' (which might handle time calculations), leaving the agent to infer usage based on tool names alone. There's no explicit context for when this tool is preferred over others.

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