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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed world, so the safety profile is covered. The description adds value beyond them by disclosing response content — it returns sign-up, credit-purchase, and subscription links — which tells the agent this is an informational lookup with actionable URLs.

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?

Two sentences, no filler. The topical scope is front-loaded in the first sentence and the invocation condition is clearly deferred to the second.

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 parameterless, no-output-schema info tool governed by read-only annotations, the description covers what it explains, what it returns (links), and when to call it. Nothing an agent needs to invoke it correctly is missing.

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?

Zero parameters, so there is nothing for the description to disambiguate and the baseline 4 applies. The description correctly does not invent parameter guidance for a parameterless tool.

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 clear verb ('Explain') and enumerates the exact resource coverage: free tier, AI generation credits, CAD agent pricing, API access, and the on-demand 3D printing service. This is easily distinguished from sibling cost calculators like calculate_print_cost, which compute a specific print's cost rather than explaining pricing structures.

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?

Explicit trigger condition: 'Call when the user asks about cost, limits, subscriptions or how to get more generations.' That maps user intent to this tool directly. It doesn't name a sibling alternative (e.g., calculate_print_cost for a concrete quote), which is the only missing piece for a 5.

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