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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered elsewhere. The description contributes the useful detail that the call returns the list together with its embedded holidays and their fields, but says nothing about volume, pagination, or what happens when listId is unknown.

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?

It is short and free of padding, which is good, but it is a sentence fragment with no main verb and the most decision-relevant information (that it fetches a list plus its holidays) is not front-loaded as an action. Brevity here reads as under-specification rather than tight structure.

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 one-parameter, read-only, idempotent tool with rich annotations, the description is minimally adequate and does cover the shape of the return value in the absence of an output schema. What is missing is any statement of when to prefer the sibling tools and any behavior for edge cases such as an invalid or unknown listId.

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?

With a single required parameter at 100% schema description coverage, the schema already explains listId including its provenance and length bounds. The description adds no further meaning about the identifier, so the baseline of 3 applies.

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 is a noun phrase, 'A custom holiday list with its holidays', so the retrieval verb is only implied by the name/title 'get_holiday_list'. It does add real substance by enumerating the returned fields (id, name, startDate, endDate), which hints at how it differs from get_holidays, but it never states that distinction 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?

There is no when-to-use guidance at all: no mention of when to call this instead of get_holidays for individual holidays, or list_holiday_lists for the catalog of lists. The only routing hint is the schema-level note that listId comes 'from list_holiday_lists', which lives in the schema, not the description.

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