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

With no annotations, the description carries the full behavioral burden. It discloses the important default that start defaults to today and clarifies that returned days are those on which clearing and settlement cannot take place, but it does not describe return format, end-date behavior, timezone handling, or whether this is a read-only lookup.

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?

The description is compact and front-loaded: purpose first, then the market identifier format, then the start default. Every clause adds useful information, though the opening noun phrase could be slightly more verb-forward for scanning.

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?

For a simple three-parameter lookup with no output schema and no annotations, the description covers the core concept, market format, and start default. It is incomplete because it says nothing about the end parameter or the response shape, which are left entirely to inference.

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 adds meaningful semantics for the market parameter by specifying ISO 10383 MIC format with an XNYS example, and it documents that start defaults to today. However, the end parameter is not described at all, leaving one of three parameters undocumented.

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 clearly identifies the resource as exchange settlement holidays scoped to a market and explains what those holidays mean. It is distinguishable from siblings like trading_holidays or bank_holidays by specifying clearing and settlement, though it does not explicitly name or contrast those alternatives.

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?

The purpose implies when to use this tool rather than alternatives such as trading_holidays or bank_holidays, but there is no explicit when-to-use or when-not-to-use guidance. The note that start defaults to today is a useful usage detail, but sibling differentiation remains implicit.

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