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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description adds genuine value beyond them: data comes from a fixed static list, there is no extrapolation past coverage, weekends alone are not events, and official notices override. Only the return shape (date? name? half-day flag?) is undisclosed.

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?

Compact and front-loaded: the core definition comes first, caveats follow. The telegraphic phrasing ('fixed MO static calendar list') is slightly opaque but no sentence is wasted.

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?

No output schema exists, so the description should indicate what 'next closure' returns (date, holiday name, half-day indicator) and it does not. For a single-param read tool the caveats are adequate, but the return contract is missing.

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?

One required parameter with 0% schema description coverage means the description carries the full burden, yet it never explains what 'exchange' should contain (e.g., MIC code, exchange name, casing, length limits). With no annotation or schema help on this field, the gap is material.

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 verb+resource: retrieves the next published exchange holiday or half-day from a fixed static calendar. It also scopes it ('MO static calendar list', weekends excluded), which lets an agent distinguish it from trading_day and trading_hours, though no sibling is named.

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?

'No extrapolation beyond coverage' and 'Official exchange notices take precedence' imply the boundary conditions and hint at the recent_notices sibling, but there is no explicit when-to-use/when-not or direct routing instruction to an alternative tool.

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