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

No annotations are supplied, so the description bears the full burden. It usefully discloses the default behavior for start (today) and clarifies what a returned day represents, but says nothing about the response shape, whether the date range is inclusive, behavior for invalid/non-convertible currency codes, or limits on range size.

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 with the core concept front-loaded and the default-value note appended where it belongs. The parenthetical currency example earns its place; only minor trimming would be possible.

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 and no annotations, the description has to carry everything. It covers the required currency parameter and the start default adequately, but leaves the end parameter and the returned structure entirely to inference, which is a real gap for a date-range query 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?

Schema description coverage is 0%, so the description must compensate. It does document currency (ISO 4217, with a USD example) and start's default, but the end parameter is never explained (inclusivity, format, or default open-endedness), leaving a third of the parameters undocumented in both places.

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 (FX market holidays) with a clear scope qualifier: for a given currency, defined as days that currency's FX market does not trade. This meaningfully separates it from bank_holidays, settlement_holidays, and trading_holidays, though it never names those siblings explicitly.

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 resource definition (ask for FX-market-specific non-trading days per currency), but there is no explicit guidance on when to prefer this over sibling tools like trading_holidays or bank_holidays, and no stated exclusions or prerequisites.

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