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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description goes further by disclosing return contents (open flag, session, current ET time, next open/close) and the underlying holiday/early-close and 24/7 venue rules an agent needs to interpret those flags — genuinely beyond the 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?

Front-loads the core question, then compresses venue schedules, return shape, and the omit rule into two dense sentences with no filler. Slightly run-on, but every clause carries information an agent needs.

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?

With no output schema, the description still enumerates the returned fields and explains the special cases (NYSE holidays, 1pm early closes, 24/7 markets), so an agent can call and interpret the result without opening anything else.

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 coverage is 100% and the single parameter is already documented with the same enum values and 'omit for all' note in the schema, so the description largely repeats the structured field. The per-venue clock table adds context about what each value means, but no new parameter-level syntax or constraints.

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 opens with the exact question the tool answers ('Is a venue open right now?') and then states the resource granularity (per-venue session clocks). No sibling tool covers market sessions, so it is trivially distinguishable from the surrounding order/portfolio tools.

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?

Usage context is clear: use it to check whether a venue is currently open, and 'Omit venue for all' tells the agent how to get a broad answer. There are no alternative tools doing this job, so no exclusions are needed, but the description never explicitly frames when to prefer per-venue vs. all.

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