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

Annotations already declare readOnly, idempotent, non-destructive and openWorld=false, so the safety profile is free. The description adds real context beyond that: no authentication is required, results carry counts, and the returned values are guaranteed consumable by pool_build_proxy_url. It doesn't say anything about ordering or handling of empty facet sets, which keeps it off 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?

Three sentences, front-loaded with the returned facet set, then the consumer relationship, then the filter behavior. Every sentence earns its place; the only minor slack is the parenthetical '(with ASN and class)' and the tacked-on 'no account needed' clause.

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 5-parameter read-only facet tool with no output schema, the description covers purpose, output contents, auth requirements and filter semantics. The remaining gap is the pool selector (peer vs mbl vs all), which is documented only in the schema and changes what stock is counted.

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 the baseline is 3; the description earns above that by explaining that the filter parameters change what 'remains' in the counts rather than merely slicing a list, and by tying returned values to the arguments pool_build_proxy_url accepts. It does not explain the pool enum semantics (peer/mbl/all), leaving that entirely to 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?

States a specific verb and resource set: 'List the cities, states, carriers (with ASN and class) and IP classes that have stock in one country, with counts.' It also ties itself to the sibling pool_build_proxy_url by naming the values it produces, so an agent can distinguish it from pool_get_stock or pool_build_proxy_url without opening either schema.

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?

Clear on two usage points: it can be called with no account, and passing city/state/carrier shows 'what remains once that filter is applied' – i.e. use it to preview narrowing before building a URL. There is no explicit when-not or a direct comparison to pool_get_stock, so it stops short of full routing guidance.

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