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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds useful content disclosure (active sessions, overlaps) but says nothing about time zone assumptions, refresh cadence, or whether the answer is real-time or cached, which matters for a live-market status check.

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?

A single sentence that front-loads the primary question (is the market open) followed by the supporting details (sessions, overlaps). Nothing redundant, and it's long enough to convey the return scope.

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 parameters, no output schema, and read-only annotations, the description carries the burden of explaining what comes back, which it does by enumerating sessions and overlap states. Only the time-zone/reference-time assumption is unaddressed, a minor gap for a status tool.

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 takes zero parameters, so there are no semantics to explain; the baseline for a no-param tool is 4. The description correctly avoids inventing parameter talk.

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 concretely states what the tool returns: forex market open status, the active sessions among Sydney/Tokyo/London/New York, and current/upcoming overlaps. It's clearly distinct from all siblings (position sizing, currency strength, calendar, quotes, screener), though the verb is implied rather than front-loaded.

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 implied by the topic (checking forex trading hours) but no explicit when-to-use, exclusions, or alternative routing is given. No sibling is named even implicitly as a contrast, so an agent must infer the context from the domain alone.

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