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

Annotations already indicate it's a write operation (readOnlyHint=false) and idempotent (idempotentHint=true). The description adds the important partial-update behavior ('Pass only fields to change'), clarifying that omitted fields retain their existing values. This goes beyond annotations without contradicting them.

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 sentences and nine words, front-loaded with the action. Every word earns its place with no filler or redundancy.

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 schema descriptions and an output schema covering parameters and return values, the description sufficiently covers the key behavioral nuance (partial update). It could be more complete by explaining how to clear a field or how recurrence fields interact, but for an update tool this is adequate.

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 descriptions cover 100% of parameters, so the baseline is 3. The description adds the key semantic that only provided fields are modified, which is not captured in the schema. However, it doesn't address how to null-out fields (e.g., passing null explicitly).

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 states the action ('Update') and resource ('service schedule window'), which distinguishes it from sibling tools like create_service_schedule and list_service_schedules. However, 'window' is slightly ambiguous without schema context, and it doesn't explicitly mention that it operates on an existing schedule by ID.

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?

No guidance is provided on when to use this tool versus alternatives. It doesn't mention that create_service_schedule is for new schedules or that update_service handles service-level changes. The phrase 'Pass only fields to change' is parameter usage guidance, not tool selection guidance.

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