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

With no annotations, the description carries the full burden. It discloses key behavioral traits: cities are grouped by metro area (e.g., 'minneapolis-mn' covers suburbs), and the list is limited to areas where verified providers operate. It does not cover output format or pagination, but the grouping and verification details add value beyond the schema.

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 three sentences, each with a clear purpose: state the operation, indicate usage, and explain grouping/filtering. It is front-loaded with the main purpose and contains 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 simple list tool with 2 parameters and no output schema, the description covers the essential context: what it lists, how to use it (before search_providers), and key output characteristics (city slugs, grouping). It could say more about return format or error handling, but given the low complexity, it is adequately complete.

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?

The input schema already describes both parameters fully (100% coverage), so baseline is 3. The description adds little beyond noting that niche_id comes from list_niches (already in schema) and that state filtering is optional. It provides an example of a city slug in the description, but that's related to output rather than parameter semantics.

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 explicitly states the tool's function: 'List available cities and metro areas where verified providers operate for a given niche.' It uses a specific verb ('list') and resource ('cities and metro areas'), and differentiates from sibling search_providers by stating its role in discovering valid city slugs before that call.

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?

Provides clear context: 'Use this to discover valid city slugs before calling search_providers.' This tells the agent when to use the tool relative to a sibling. It does not explicitly mention when not to use or list alternatives, so it lacks full exclusion guidance, but the direction is explicit.

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