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

Annotations already signal read-only/non-destructive behavior; the description adds important behavior beyond that: shared-cache vs fresh-fetch semantics, the effect of max_age=0, the fact that the response body is never returned, and the full list of returned fields. This gives an agent an accurate model of what happens at call time.

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 core purpose is front-loaded in the first sentence, and the remaining sentences efficiently convey freshness control and the key exclusion ('response body itself is not returned'). No filler or repetition.

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?

Even without an output schema, the description enumerates all relevant return fields and explicitly states the body is not returned. For a two-parameter tool with safe annotations, this is complete enough for an agent to invoke it correctly without further inference.

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?

Both parameters are fully documented in the schema (100% coverage), so the description does not need to compensate. It reinforces the max_age=0 behavior already in the schema and adds the cache-vs-fresh nuance, but the incremental meaning over the schema is modest.

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: 'Buy a timestamped FreshProof observation of a public HTTP/HTTPS URL', immediately distinguishing it from the only sibling (freshproof_info). It also enumerates exactly what is returned, so there is no ambiguity about what the tool does.

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?

The description gives clear operational guidance: use max_age=0 when a fresh public-network request is required, and otherwise an older cached observation is acceptable. It does not explicitly contrast with freshproof_info or state when not to use this tool, so it stops short of a 5.

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