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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds non-obvious return context — that the response embeds the message thread and associated users — which is genuinely useful for an agent deciding whether one call suffices.

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?

One compact sentence plus a short endpoint reference; the key behavior (fetch one by id, includes thread and users) is front-loaded with zero filler.

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 one fully documented parameter, no output schema, and readOnlyHint covering safety, the description is nearly sufficient on its own; the mention of the embedded message thread and users compensates for the missing output schema.

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 100% and the single request_id parameter is fully documented there, so the baseline is 3. The description only restates that lookup is by id and adds no format or constraint detail beyond the schema.

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 (Fetch) and resource (one time-off request) with the retrieval key (by id), which cleanly separates it from the sibling wheniwork_list_time_off_requests. It also names the upstream endpoint, leaving no ambiguity about what the tool does.

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 'one ... by id' phrasing implies this is the single-record lookup versus the list tool, but no explicit when-to-use or when-not-to-use guidance is given. Usage must be inferred from the singular/plural naming and the required id.

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