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

Annotations already state readOnlyHint, openWorldHint, and idempotentHint. The description adds value by listing the possible status values, which informs the agent about expected return states without contradicting the 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?

The description is a single concise sentence, front-loaded with the verb 'check' and resource, and efficiently lists statuses. Every word contributes to clarity with no 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?

For a simple read-only tool with one parameter and no output schema, the description provides sufficient context: it states what the tool does and enumerates the possible return statuses, which act as the expected output. Annotations cover safety and idempotency concerns.

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 only parameter 'sessionId' with a clear description ('Checkout session ID'), achieving 100% schema description coverage. The tool description does not add further parameter semantics beyond the schema, so 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 uses a specific verb 'check' and identifies the resource 'payment status of a checkout session'. It also enumerates possible statuses (pending, verifying, confirmed, expired, failed), making the tool's purpose unambiguous and distinct from siblings like create_checkout or pay_merchant.

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?

No explicit when-to-use or alternative guidance is provided. The description implies usage (checking payment status) but does not contrast with related tools like verify_receipt or check_paywall, so the agent must infer appropriate usage from context.

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