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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety and external-lookup profile is covered. The description adds one piece of genuinely new context, that the address is 'looked up and cached' (a geocoding side effect), and that only 'active' zones are matched. It says nothing about what comes back or behavior when no zone matches.

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?

A single sentence that front-loads the outcome ('which active service zones contain a place') and follows with the inputs. No filler, though the colon+clause structure makes the input modes slightly dense to parse.

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 no output schema, 0% schema coverage, and zero required parameters, the description leaves key questions open: what is returned (zone id, name, distance?), whether both lat and lng are required together, and what an empty result means. For a geo-lookup tool with three undocumented params, more is needed.

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 0% for 3 parameters, so the description must carry the load. It does clarify that address is geocoded/cached and that lat+lng is an alternative path, which is more than the bare schema says. However, it never states that lat and lng must be supplied together, nor what happens if both address and coordinates are given.

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+resource: 'Which active service zones contain a place.' That is clear and does not overlap with list_service_zones (enumerate zones) or nearest_technicians (people). It stops short of naming the sibling it is closest to, so it is clear but not fully differentiated.

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 implies usage by offering two input modes ('pass an address ... or lat + lng'), which tells the agent what it needs to supply. But there is no guidance on when to prefer this over list_service_zones, reverse_geocode, or nearest_technicians, and no exclusions.

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