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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description adds genuinely new behavior: the $0.02 cost, refusal of private/local hosts and malformed URLs, and the guarantee that unreachable/upstream failures are surfaced explicitly rather than fabricated. The anti-hallucination guarantee is exactly the kind of trait an agent cannot infer from annotations.

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 tight sentences, front-loaded with cost and purpose, then scope, then return values and failure semantics. Every clause carries information and none is redundant.

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 carries the burden of describing returns and does so (reachability, HTTP status, latency, risk flags, SHA-256 evidence) plus failure behavior. An agent has everything needed to decide and call correctly.

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% with a single documented 'url' parameter, so the baseline is 3. The description's mention of rejecting private/local hosts and malformed URLs restates the schema constraint rather than adding new parameter syntax or format guidance.

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+resource ('read-only endpoint preflight') with scope ('before an agent depends on or pays an unfamiliar API, webhook or URL') that clearly separates it from siblings like moneygrid_fetch (which presumably fetches) and gridverify_evidence.

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?

Gives an explicit trigger condition — use it before depending on or paying for an unfamiliar endpoint — which is unusually actionable. It stops short of naming an alternative tool or spelling out when-not to use it (the private/local rejection is a constraint, not a routing rule), so it falls just short of the top band.

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