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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description meaningfully adds that availability is a function of which workers operate near the address, hinting that results reflect a real-world supply condition rather than a static lookup. It does not cover latency, caching or any auth context, hence not a 5.

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 tight sentences with no filler, and the action plus its sequencing constraint are front-loaded. The second sentence earns its place by justifying why a separate check exists.

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?

There is no output schema, and the description's wording ('check whether a service is available') implicitly conveys a boolean-ish availability result, which is enough for an agent to act. It could be slightly more explicit about what an unavailable answer means for next steps, but nothing critical is missing for a read-only two-parameter check.

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 service enum is fully documented in the schema, so the schema carries the parameter burden. The description only gestures at the 'service' parameter ('a service is available') and adds no format or default detail beyond what the schema already states, so the baseline 3 is appropriate.

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 ('check') and resource ('service availability at a Singapore postal code') and situates the call in the workflow ('before looking for times'), which cleanly separates it from siblings like find_times and find_services. The added 'coverage depends on which cleaners or technicians work near the address' explains the underlying notion of coverage rather than just restating the name.

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?

Gives clear ordering guidance ('before looking for times'), which tells an agent when to reach for this tool rather than jumping straight to find_times. It does not name alternatives explicitly or state any exclusion conditions, so it stops short of a full when/when-not/alternatives treatment.

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