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

Annotations already indicate readOnlyHint=false and openWorldHint=true, signaling a non-read operation with external effects. The description adds valuable behavioral context: 'Requires active subscription' and 'Does not count toward your monthly searches', which go beyond annotation defaults and clarify the transactional nature.

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 description is extremely concise: two sentences with no filler. It front-loads the core action ('Buy Search Pack') and adds necessary constraints and benefits in an efficient manner.

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 simple one-parameter tool with good annotations and complete schema, the description is largely sufficient. It would benefit from stating that the tool returns a payment link (as implied by the name), but the lack of an output schema makes this a minor gap. Overall, it is complete for intended use.

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?

The schema covers the 'quantity' parameter fully with a description and default. The tool description adds product details like price and expiration but does not add meaning to the parameter itself. Since schema description coverage is 100%, a score of 3 is appropriate.

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?

The description clearly states the action: 'Buy Search Pack', with specific details like price ($5), quantity (50 searches), and conditions (requires active subscription). It is specific and distinguishes itself from sibling tools like get_upgrade_link by focusing on purchasing a pack rather than upgrading a subscription.

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 provides clear context for when to use this tool: when you have an active subscription and need additional searches. It also notes that it 'does not count toward your monthly searches', implying a quota-related use case. However, it does not explicitly name alternatives or state when not to use it, so it falls 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.