calendar_open_today

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 only states '[FREE] Current day equity market schedule,' which does not explain what output to expect, timezone handling, or whether it returns open/close times or just open/closed status. This is insufficient for the agent to understand the tool's behavior.

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 extremely brief and compact, but it is more under-specified than truly concise. It is a noun phrase fragment rather than a complete sentence, and a structured description with a verb would be more effective without adding much length.

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?

Despite being a simple zero-parameter tool, the description is not complete enough. It does not clarify whether the schedule includes market hours, holidays, or just open/close status, and there is no output schema to fill the gap. This leaves significant ambiguity about the tool's result.

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 tool has zero parameters, so the baseline of 4 applies. The description does not need to explain parameter meanings, and no parameter information is missing.

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 identifies the resource ('equity market schedule') and scope ('current day'), distinguishing it from siblings like calendar_on_date and calendar_year. However, it lacks an explicit verb (e.g., 'get') and does not specify what 'schedule' includes (open/close times, holidays, status).

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 usage for today's schedule through the phrase 'current day', but it does not explicitly state when to use this tool versus calendar_on_date or calendar_year. No exclusions or alternatives are mentioned.

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