get_market_hours

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint), so the bar is lower. The description adds genuine behavioral context by disclosing the return semantics — session breakdown per day plus an active `session_now` field for today only — which the annotations do not convey.

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?

Two tight sentences, zero filler, with the core capability front-loaded and the today-only `session_now` caveat following. Every clause earns its place.

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?

An output schema exists, so the description is not obligated to explain return values, and what it does state (sessions, open flag, session_now) is sufficient for an agent to invoke the tool correctly. The remaining gap is the undocumented `markets` parameter, which is a minor completeness shortfall rather than a blocker.

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 coverage is only 50%: `date` documents its format ('YYYY-MM-DD, default today'), but `markets` has no description anywhere, including the description text. The description mentions neither parameter, so it does not compensate for the undocumented `markets` enum list (equity, option, bond, future, forex) or its default behavior.

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?

States a specific resource (trading sessions: pre-market, regular, post-market) and a specific clarification (whether the market is open), so an agent immediately knows what it returns. It does not explicitly name or contrast with siblings, but the purpose is distinct enough that differentiation is unnecessary.

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 is only implied: an agent can infer this is for checking market open/closed state and session boundaries. There is no explicit when-to-use, when-not-to-use, or reference to alternatives such as get_current_time, which is the nearest sibling an agent might confuse it with.

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