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

Annotations already declare readOnlyHint, openWorldHint, and non-destructive behavior, so the description is not responsible for the safety profile. It adds useful behavioral context by stating that results include ids and occurrence counts and by specifying the GET path, though it does not discuss pagination or rate limits.

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?

The description is compact and front-loads the resource scope before listing filter-field mappings and the endpoint. Every sentence contributes useful information with no filler.

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 read-only, schema-complete listing tool with annotations covering safety, the description is largely complete. It explains the returned data and filter mappings, though it could mention prerequisites such as deriving idx_id from idx_list_approved_mls, which is only covered in the schema.

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 coverage is 100%, so parameter basics are already documented. The description adds meaningful semantics by mapping which filter fields are valid for cities, counties, and postalcodes, which goes beyond the schema's broader note that filter_field must fit kind.

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 identifies the resource as cities, counties, or postal codes present in an MLS's data, and notes the ids and occurrence counts returned. It is distinguishable from siblings like idx_list_mls_property_types and idx_list_mls_search_fields by resource type, though it does not explicitly name alternatives.

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?

The description explains what data is available and maps filter fields to each kind, but it gives no explicit guidance on when to choose this tool over siblings or what prerequisites apply. Usage must be inferred from the purpose rather than stated.

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