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

Annotations already declare readOnlyHint=false, destructiveHint=true and idempotentHint=false, so the safety profile is covered. The description adds valuable non-obvious context: the call is a read-modify-write that sends the absence back unchanged except for status, plus the required permission and the underlying PUT endpoint. It does not explain the notify_employee side effect or failure modes.

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?

Three terse sentences with the WRITE prefix and the core verb front-loaded; the permission caveat and endpoint come after. No sentence is filler and it is far shorter than the schema it accompanies.

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 mutation tool with full annotation coverage, a 100%-documented schema and no output schema, the description supplies the missing pieces an agent needs: write semantics, permission requirement, and the mutate-one-field behavior. It is essentially complete, missing only any note on the notify_employee default or error behavior.

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 all three parameters are documented in-schema, so the baseline is 3. The description adds one useful nuance — that 'decision' changes only the status field and the rest of the record is sent back unchanged — but contributes nothing about notify_employee or id range.

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 leads with a specific verb pair and resource ('approve or decline an absence request') and adds a WRITE marker, making it trivially distinguishable from siblings like shiftbase_get_absence or shiftbase_request_absence. An agent can identify the operation without opening the schema.

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?

It states the permission prerequisite ('needs the approve-absence permission') and implies the correct context (an existing absence awaiting a decision), which is enough to select the tool. It never names an alternative tool or an explicit when-not condition, so it falls short of full routing guidance.

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