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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the safety profile is covered by structured data. The description adds one genuinely non-redundant fact — the required service_areas:write scope — but does not explain what makes an update 'destructive' (e.g., whether omitted fields are cleared) or how missing fields are treated.

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 short sentences, front-loaded with the action and target, with zero filler. Every clause carries information an agent needs.

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 7-parameter mutation tool with full schema coverage and no output schema, the description is minimally adequate: schema handles parameters and annotations handle safety. It leaves gaps around partial-update semantics and routing to sibling service-area tools, which are material for a write operation.

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%, so all seven parameters are already documented in the schema; the baseline is 3. The description only reiterates that lookup is "by ID," adding no format, constraint, or optionality 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?

The description states a specific verb and resource ("Update an existing service area by ID"), which is unambiguous. It does not, however, distinguish this from sibling operations such as create_service_area, delete_service_area, or update_service_area_site, so an agent must infer routing from the name alone.

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 guidance on when to use this tool versus alternatives like bulk_update or the related service-area-site/system-class update tools, nor any note on partial vs full updates. The only contextual hint is the scope prerequisite, which is an authorization condition rather than usage guidance.

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