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

Beyond the annotations (readOnlyHint=false, openWorldHint=true), the description discloses critical behavioral details: Polar is the Merchant of Record, the card payment requires a human, the claim_token must be kept private, and the returned URL must be presented to an operator. These are significant operational facts not visible in annotations or schema.

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 concise and well-structured: the first sentence states the core purpose, and the second sentence provides essential workflow context. Every sentence adds value with no filler or redundancy.

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 covers the key context: what the tool creates, how it fits into the larger flow (including estimate, status polling, and key claiming), the human-in-the-loop requirement, and the privacy of the claim_token. With an output schema present, the description is complete for this tool's complexity.

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 already provides 100% coverage for the single 'email' parameter with format and description. The tool description does not add further parameter details, but the schema is sufficient, so a baseline 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 tool's function: 'Create a loginless Polar Checkout URL for MockHero's metered agent plan.' It uses a specific verb and resource, and distinguishes it from siblings like check_agent_checkout_status and claim_agent_api_key by focusing on the creation step.

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 explicit workflow guidance: it tells the user to combine the returned URL with estimate_agent_usage cost, keep the claim_token private, poll check_agent_checkout_status, and call claim_agent_api_key after payment. This clearly indicates when to use this tool relative to alternatives and the recommended sequence.

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