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

Goes well beyond the readOnly/idempotent annotations: 'Local, no network', an explicit warning that 'The result contains the password', the sticky-holds-device-not-IP caveat, and the rule that sticky/hard/auto* only persist across connections with a sid. These are non-obvious behavioral facts an agent could not infer from structured fields.

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?

Front-loaded with the core action and host, then layered prerequisites, pool meanings and rotation semantics. The middle rotation sentence is dense and runs long, but for 17 parameters with meaningful enums the length is largely earned; little is 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?

With no output schema, the description does tell the agent the result contains a URL plus the password, though it doesn't say the exact return shape. Combined with full schema coverage and rich rotation/pool explanation, an agent has enough to call it correctly; only the precise return structure is unstated.

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 already 100%, so the baseline is 3, but the description adds cross-parameter semantics the schema cannot express: the pool enum's real-world meaning ('mbl' = carrier modems in a fixed country list, 'any'/'best' = gateway chooses), rotation mode behavior, and the sid dependency for persistence. The asn/isp/failover/strict interactions are left 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 — 'Build a ready-to-use Pool Gateway proxy URL' — and immediately names the host and ports (gw.proxies.sx, 7000/7001). No sibling tool builds URLs, and the description makes that scope unmistakable.

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 routes the agent to prerequisites ('Take proxyUsername and password from pool_get_my_credentials') and to pool_get_facets for city/state/carrier values, which is genuine usage guidance. It doesn't state when NOT to use this tool (e.g. when a plain status check suffices), but for a builder tool the context is largely covered.

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