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

With no annotations, the description carries the disclosure burden and does well: it states exactly one request is made from the provider's servers, that private/localhost targets are refused (SSRF protection), that the operation is read-only server-side, and that an operator key is required. It omits redirect/timeout behavior and what 'something sensible' means as a result, keeping it from 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 short sentences, zero filler, and the key scoping facts (prerequisite step, SSRF refusal, auth requirement) are all front-loaded. Nothing is padded.

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?

The description adequately covers safety profile and sequencing for a no-output-schema probe, but with 0% schema coverage on three parameters and a nested headers object, it leaves the agent without guidance on what method/headers do or what a passing vs. failing probe looks like. Adequate but with clear gaps.

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 three parameters, so the description must compensate and does not. upstream_url is only alluded to indirectly, and upstream_method (with its GET/POST/PUT/DELETE enum) and upstream_headers (a nested object with real security implications when probing arbitrary URLs) are never addressed.

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 (test/probe reachability) on a specific resource (a URL to be sold), and anchors it in the gateway_* family by naming gateway_register as the follow-on step. An agent can distinguish it from gateway_register/gateway_catalog without opening any 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?

Clearly positions the tool as a pre-flight check 'before gateway_register', which gives explicit sequencing context. It does not state when to skip it or name other alternatives, so it stops short of a full when/when-not rubric.

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